@article {A-K-N-S,
    AUTHOR = {Ablowitz, M. J. and Kaup, D. J. and Newell, A. C. and Segur, H.},
     TITLE = {Method for solving the sine-{G}ordon equation},
   JOURNAL = {Phys. Rev. Lett.},
  FJOURNAL = {Physical Review Letters},
    VOLUME = {30},
      YEAR = {1973},
     PAGES = {1262--1264},
       DOI = {10.1103/PhysRevLett.30.1262},
       URL = {https://doi.org/10.1103/PhysRevLett.30.1262},
}

@article {Ai-1983,
    AUTHOR = {Aiyer, Raju N.},
     TITLE = {Recursion operators for infinitesimal transformations and
              their inverses for certain nonlinear evolution equations},
   JOURNAL = {J.~Phys.~A},
  FJOURNAL = {Journal of Physics. A. Mathematical and General},
    VOLUME = {16},
      YEAR = {1983},
    NUMBER = {2},
     PAGES = {255--262},
       DOI = {10.1088/0305-4470/16/2/008},
       URL = {https://doi.org/10.1088/0305-4470/16/2/008},
}

@mics {Bab-1996,
    AUTHOR = {Babich, M. V.},
     TITLE = {Methods of the theory of sine-{G}ordon equation and the {V}oss surfaces},
      NOTE = {{P}reprint NTZ 46/1996, Universit\"at Leipzig, Zentrum f\"ur H\"ohere Studien, 1996, \url{https://cds.cern.ch/record/320244/files/SCAN-9702082.pdf}},
}

@book {Bia-I,
    AUTHOR = {Bianchi, L.},
     TITLE = {Lezioni di geometria differenziale. {V}ol.~I},
 PUBLISHER = {E.~Spoerri, Pisa},
      YEAR = {1894},
     PAGES = {viii+541},
}

@book {Bia-II,
    AUTHOR = {Bianchi, L.},
     TITLE = {Lezioni di geometria differenziale. {V}ol.~II},
 PUBLISHER = {E.~Spoerri, Pisa},
      YEAR = {1903},
     PAGES = {iv+605},
}

@book {B-V-V,
    AUTHOR = {Bocharov, A. V. and Chetverikov, V. N. and Duzhin, S. V. and
              Khorkova, N. G. and Krasilshchik, I. S. and
              Samokhin, A. V. and Torkhov, Yu. N. and Verbovetsky, A. M. and
              Vinogradov, A. M.},
     TITLE = {Symmetries and conservation laws for differential equations of
              mathematical physics},
    SERIES = {Transl. Math. Monogr.},
    VOLUME = {182},
 PUBLISHER = {American Mathematical Society, Providence, RI},
      YEAR = {1999},
     PAGES = {xiv+333},
       DOI = {10.1090/mmono/182},
       URL = {https://doi.org/10.1090/mmono/182},
}

@article {JC-FC-AF-1917,
    AUTHOR = {Cen, J. and Correa, F. and Fring, A.},
     TITLE = {Degenerate multi-solitons in the sine-{G}ordon equation},
   JOURNAL = {J.~Phys.~A},
  FJOURNAL = {Journal of Physics. A. Mathematical and General},
    VOLUME = {50},
      YEAR = {2017},
     PAGES = {435201, 20~pages},
       DOI = {10.48550/arXiv.1705.04749},
       URL = {https://doi.org/10.48550/arXiv.1705.04749},
    EPRINT = {nlin.SI/1705.04749},
}

@article {D-S-2008,
    AUTHOR = {Demskoi, D. K. and Sokolov, V. V.},
     TITLE = {On recursion operators for elliptic models},
   JOURNAL = {Nonlinearity},
  FJOURNAL = {Nonlinearity},
    VOLUME = {21},
      YEAR = {2008},
     PAGES = {1253--1264},
       DOI = {10.48550/arXiv.nlin/0607071},
       URL = {https://doi.org/10.48550/arXiv.nlin/0607071},
    EPRINT = {nlin.SI/0607071},
}

@phdthesis {JBD-1913,
    AUTHOR = {Diller, J. B.},
     TITLE = {\"Uber die den {E}nneperschen {F}l\"achen konstanten negativen
{K}rummungsmasses entsprechenden {V}o{\ss}schen {F}l\"achen},
      NOTE = {{U}niversit\"at W\"urzburg, 1913},
}

@article {UD-1870,
    AUTHOR = {Dini, U.},
     TITLE = {Sopra alcune formole generali della teoria delle superficie,
e loro applicazioni},
   JOURNAL = {Ann. Mat. Pura Appl.},
  FJOURNAL = {Annali di Matematica},
    VOLUME = {4},
      YEAR = {1870},
     PAGES = {175--206},
       DOI = {10.1007/BF02420031},
       URL = {https://doi.org/10.1007/BF02420031},
}

@article {D-B-1977,
    AUTHOR = {Dodd, R. K. and Bullough, R. K.},
     TITLE = {Polynomial conserved densities for the sine-{G}ordon
              equations},
   JOURNAL = {Proc. Roy. Soc. London Ser.~A},
  FJOURNAL = {Proceedings of the Royal Society. London. Series A.
              Mathematical, Physical and Engineering Sciences},
    VOLUME = {352},
      YEAR = {1977},
    NUMBER = {1671},
     PAGES = {481--503},
       DOI = {10.1098/rspa.1977.0012},
       URL = {https://doi.org/10.1098/rspa.1977.0012},
}

@incollection {AD-1999,
    AUTHOR = {Doliwa, Adam},
     TITLE = {Integrable discrete geometry with ruler and compass},
 BOOKTITLE = {Symmetries and {I}ntegrability of {D}ifference {E}quations ({C}anterbury, 1996)},
    SERIES = {London Math. Soc. Lecture Note Ser.},
    VOLUME = {255},
     PAGES = {122--136},
 PUBLISHER = {Cambridge University Press, Cambridge},
      YEAR = {1999},
       DOI = {10.1017/CBO9780511569432.011},
       URL = {https://doi.org/10.1017/CBO9780511569432.011},
}

@article {LPE-1906,
    AUTHOR = {Eisenhart, Luther Pfahler},
     TITLE = {Associate surfaces},
   JOURNAL = {Math. Ann.},
  FJOURNAL = {Mathematische Annalen},
    VOLUME = {62},
      YEAR = {1906},
    NUMBER = {4},
     PAGES = {504--538},
       DOI = {10.1007/BF01449817},
       URL = {https://doi.org/10.1007/BF01449817},
}

@book {LPE-1909,
    AUTHOR = {Eisenhart, Luther Pfahler},
     TITLE = {A treatise on the differential geometry of curves and
              surfaces},
 PUBLISHER = {Ginn, Boston},
      YEAR = {1909},
     PAGES = {xiv+474},
}

@article {LPE-1914,
    AUTHOR = {Eisenhart, Luther Pfahler},
     TITLE = {Transformations of surfaces of~{V}oss},
   JOURNAL = {Trans. Amer. Math. Soc.},
  FJOURNAL = {Transactions of the American Mathematical Society},
    VOLUME = {15},
      YEAR = {1914},
    NUMBER = {3},
     PAGES = {245--265},
       DOI = {10.2307/1988587},
       URL = {https://doi.org/10.2307/1988587},
}

@article {LPE-1915,
    AUTHOR = {Eisenhart, Luther Pfahler},
     TITLE = {Conjugate systems with equal point invariants},
   JOURNAL = {Ann. of Math.},
  FJOURNAL = {Annals of Mathematics. Second Series},
    VOLUME = {18},
      YEAR = {1916},
    NUMBER = {1},
     PAGES = {7--17},
       DOI = {10.2307/2007145},
       URL = {https://doi.org/10.2307/2007145},
}

@article {LPE-1917,
    AUTHOR = {Eisenhart, Luther Pfahler},
     TITLE = {Certain surfaces of {V}oss and surfaces associated with them},
   JOURNAL = {Rend. Circ. Mat. Palermo},
  FJOURNAL = {Rendiconti del Circolo Matematico di Palermo},
    VOLUME = {42},
      YEAR = {1917},
     PAGES = {145--166},
       DOI = {10.1007/BF03014896},
       URL = {https://doi.org/10.1007/BF03014896},
}

@book {SF-1939,
    AUTHOR = {Finikoff, M. S.},
     TITLE = {D\'eformation \`a r\'eseau conjugu\'e persistant et
              probl\`emes g\'eom\'etriques qui s'y rattachent},
    SERIES = {M\'emor. Sci. Math.},
    VOLUME = {96},
 PUBLISHER = {Gauthier, Paris},
      YEAR = {1939},
     PAGES = {92~pages},
}

@article {BG-1926,
    AUTHOR = {Gambier, Bertrand},
     TITLE = {D\'eformation continue d'un h\'elico\"{\i}de en h\'elico\"{\i}de avec r\'eseau
conjugu\'e permanent},
   JOURNAL = {Bull. Sci. Math.},
  FJOURNAL = {Bulletin des Sciences Math\'ematiques},
    VOLUME = {50},
      YEAR = {1926},
     PAGES = {308--328},
}

@article {BG-1927,
    AUTHOR = {Gambier, Bertrand},
     TITLE = {Surfaces de {V}oss et {G}uichard: {S}urfaces associ\'ees et
              adjointes. {D}\'eformation avec r\'eseau conjugu\'e
              permanent},
   JOURNAL = {Acta Math.},
  FJOURNAL = {Acta Mathematica},
    VOLUME = {51},
      YEAR = {1928},
    NUMBER = {1},
     PAGES = {83--131},
       DOI = {10.1007/BF02545661},
       URL = {https://doi.org/10.1007/BF02545661},
}

@article {BG-1931,
    AUTHOR = {Gambier, Bertrand},
     TITLE = {Surfaces de~{V}oss--{G}uichard},
   JOURNAL = {Ann. Sci. \'{E}cole Norm. Sup.},
  FJOURNAL = {Annales Scientifiques de l'\'{E}cole Normale Sup\'erieure.
              Troisi\`eme S\'erie},
    VOLUME = {48},
      YEAR = {1931},
     PAGES = {359--396},
       DOI = {10.24033/asens.813},
       URL = {https://doi.org/10.24033/asens.813},
}

@article {CG-1890a,
    AUTHOR = {Guichard, C.},
     TITLE = {Sur une classe particuli\`ere d'\'equations aux
              d\'eriv\'ees partielles dont les invariants sont
              \'egaux},
   JOURNAL = {Ann. Sci. \'{E}cole Norm. Sup.},
  FJOURNAL = {Annales Scientifiques de l'\'{E}cole Normale Sup\'erieure.
              Troisi\`eme S\'erie},
    VOLUME = {7},
      YEAR = {1890},
     PAGES = {19--22},
}

@article {CG-1890b,
    AUTHOR = {Guichard, C.},
     TITLE = {Recherches sur les surfaces \`a courbure totale constante et
              sur certaines surfaces qui s'y rattachent},
   JOURNAL = {Ann. Sci. \'{E}cole Norm. Sup.},
  FJOURNAL = {Annales Scientifiques de l'\'{E}cole Normale Sup\'erieure.
              Troisi\`eme S\'erie},
    VOLUME = {7},
      YEAR = {1890},
     PAGES = {233--264},
}

@phdthesis {GAG-1993,
    AUTHOR = {Guthrie, G. A.},
     TITLE = {Miura transformations and symmetry groups of differential equations},
      NOTE = {{U}niversity Canterbury, 1993, \url{https://ir.canterbury.ac.nz/server/api/core/bitstreams/43340926-fe51-4a80-9113-2bded2ddd046/content}},
}

@article {GAG-1994,
    AUTHOR = {Guthrie, G. A.},
     TITLE = {Recursion operators and non-local symmetries},
   JOURNAL = {Proc. Roy. Soc. London Ser.~A},
  FJOURNAL = {Proceedings of the Royal Society. London. Series A.
              Mathematical, Physical and Engineering Sciences},
    VOLUME = {446},
      YEAR = {1994},
    NUMBER = {1926},
     PAGES = {107--114},
       DOI = {10.1098/rspa.1994.0094},
       URL = {https://doi.org/10.1098/rspa.1994.0094},
}

@article {H-Kh-P-2016,
    AUTHOR = {Habibullin, I. T. and Khakimova, A. R. and Poptsova, M. N.},
     TITLE = {On a method for constructing the {L}ax pairs for nonlinear
              integrable equations},
   JOURNAL = {J.~Phys.~A},
  FJOURNAL = {Journal of Physics. A. Mathematical and Theoretical},
    VOLUME = {49},
      YEAR = {2016},
    NUMBER = {3},
     PAGES = {035202, 35~pages},
       DOI = {10.1088/1751-8113/49/3/035202},
       URL = {https://doi.org/10.1088/1751-8113/49/3/035202},
    EPRINT = {1506.02563},
}

@mics {HKF,
    AUTHOR = {Hundertwasser, F.},
     TITLE = {Hundertwasser koru flag},
      NOTE = {Hundertwasser Art Centre, Whang\=arei,
New Zealand, \url{https://www.hundertwasserartcentre.co.nz/about/hundertwasser/hundertwasser-koru-flag/}},
}

@mics {Izm,
    AUTHOR = {Izmestiev, I. and Raffaeli, M. and Rasoulzadeh, A.},
     TITLE = {Smooth, discrete, and semi-discrete {V}oss surfaces},
      NOTE = {{i}n preparation},
}

@article {NGK-1988,
    AUTHOR = {Khor'kova, N. G.},
     TITLE = {Conservation laws and nonlocal symmetries},
   JOURNAL = {Math. Notes},
  FJOURNAL = {Math. Notes},
    VOLUME = {44},
      YEAR = {1988},
    NUMBER = {1--2},
     PAGES = {562--568},
       DOI = {10.1007/BF01158125},
       URL = {https://doi.org/10.1007/BF01158125},
}

@article {KNRRS-2024,
    AUTHOR = {Kilian, M. and Nawratil, G. and Raffaelli, M. and Rasoulzadeh,
              A. and Sharifmoghaddam, K.},
     TITLE = {Interactive design of discrete {V}oss nets and simulation of
              their rigid foldings},
   JOURNAL = {Comput. Aided Geom. Design},
  FJOURNAL = {Computer Aided Geometric Design},
    VOLUME = {111},
      YEAR = {2024},
     PAGES = {102346, 24~pages},
       DOI = {10.1016/j.cagd.2024.102346},
       URL = {https://doi.org/10.1016/j.cagd.2024.102346},
}

@article {K-K-2002,
    AUTHOR = {Konno, Kimiaki and Kakuhata, Hiroshi},
     TITLE = {A fused hierarchy},
   JOURNAL = {Rep. Math. Phys.},
  FJOURNAL = {Reports on Mathematical Physics},
    VOLUME = {49},
      YEAR = {2002},
    NUMBER = {2--3},
     PAGES = {239--248},
       DOI = {10.1016/S0034-4877(02)80022-2},
       URL = {https://doi.org/10.1016/S0034-4877(02)80022-2},
}

@article {AVK-2020,
    AUTHOR = {Kostin, A. V.},
     TITLE = {On~{D}ini helicoids in the~{M}inkowski space},
   JOURNAL = {J.~Math. Sci.},
  FJOURNAL = {Journal of Mathematical Sciences},
    VOLUME = {276},
      YEAR = {2023},
     PAGES = {517--524},
       DOI = {10.1007/s10958-023-06772-9},
       URL = {https://doi.org/10.1007/s10958-023-06772-9},
}

@article {SDK-ROP-2023,
    AUTHOR = {Koval, S. D. and Popovych, R. O.},
     TITLE = {Point and generalized symmetries of the heat equation revisited},
   JOURNAL = {J.~Math. Anal. Appl.},
  FJOURNAL = {Journal of Mathematical Analysis and Applications},
    VOLUME = {527},
      YEAR = {2023},
     PAGES = {127430, 21~pages},
       DOI = {10.1016/j.jmaa.2023.127430},
       URL = {https://doi.org/10.1016/j.jmaa.2023.127430},
    EPRINT = {2208.11073},
}

@book {ISK-PHMK-2000,
    AUTHOR = {Krasil'shchik, I. S. and Kersten, P. H. M.},
     TITLE = {Symmetries and recursion operators for classical and
supersymmetric differential equations},
    SERIES = {Math. Appl.},
    VOLUME = {507},
 PUBLISHER = {Springer, Dordrecht},
      YEAR = {2000},
     PAGES = {xvi+384},
       DOI = {10.1007/978-94-017-3196-6},
       URL = {https://doi.org/10.1007/978-94-017-3196-6},
}

@book {JK-AV-RV-2017,
    AUTHOR = {Krasil'shchik, Joseph and Verbovetsky, Alexander and Vitolo,
              Raffaele},
     TITLE = {The symbolic computation of integrability structures for
              partial differential equations},
    SERIES = {Texts Monogr. Symbol. Comput.},
 PUBLISHER = {Springer, Cham},
      YEAR = {2017},
     PAGES = {xv+263},
       DOI = {10.1007/978-3-319-71655-8},
       URL = {https://doi.org/10.1007/978-3-319-71655-8},
}

@article {ISK-AMV-1989,
    AUTHOR = {Krasil'shchik, I. S. and Vinogradov, A. M.},
     TITLE = {Nonlocal trends in the geometry of differential equations:
              symmetries, conservation laws, and {B}\"acklund
              transformations},
   JOURNAL = {Acta Appl. Math.},
  FJOURNAL = {Acta Applicandae Mathematicae},
    VOLUME = {15},
      YEAR = {1989},
    NUMBER = {1--2},
     PAGES = {161--209},
       DOI = {10.1007/BF00131935},
       URL = {https://doi.org/10.1007/BF00131935},
}

@article {RL-RC-2018,
    AUTHOR = {Lin, R. and Conte, R.},
     TITLE = {On a surface isolated by Gambier},
   JOURNAL = {J.~Nonlinear Math. Phys.},
  FJOURNAL = {Journal of Nonlinear Mathematical Physics},
    VOLUME = {25},
      YEAR = {2018},
     PAGES = {509--514},
       DOI = {10.48550/arXiv.1805.10450},
       URL = {https://doi.org/10.48550/arXiv.1805.10450},
    EPRINT = {1805.10450},
}

@article {L-C-1993,
    AUTHOR = {Lou, S. Y. and Chen, W. Z.},
     TITLE = {Inverse recursion operator of the {AKNS} hierarchy},
   JOURNAL = {Phys. Lett.~A},
  FJOURNAL = {Physics Letters. A},
    VOLUME = {179},
      YEAR = {1993},
    NUMBER = {4--5},
     PAGES = {271--274},
       DOI = {10.1016/0375-9601(93)90677-R},
       URL = {https://doi.org/10.1016/0375-9601(93)90677-R},
}

@article {L-H-L-2021,
    AUTHOR = {Lou, S. Y. and Hu, X. B. and Liu, Q. P.},
     TITLE = {Duality of positive and negative integrable hierarchies via
              relativistically invariant fields},
   JOURNAL = {J.~High Energy Phys.},
  FJOURNAL = {Journal of High Energy Physics},
    VOLUME = {2021},
      YEAR = {2021},
    NUMBER = {7},
     PAGES = {no.~7, 058, 21~pages},
       DOI = {10.1007/jhep07(2021)058},
       URL = {https://doi.org/10.1007/jhep07(2021)058},
    EPRINT = {2103.04549},
}

@article {P-M-2007,
    AUTHOR = {Popov, A. G. and Maevskii, E. V.},
     TITLE = {Analytical approaches to the study of the sine-{G}ordon equation and pseudospherical surfaces},
   JOURNAL = {J.~Math. Sci},
  FJOURNAL = {Journal of Mathematical Sciences},
    VOLUME = {142},
      YEAR = {2007},
     PAGES = {2377--2418},
       DOI = {10.1007/s10958-007-0183-5},
       URL = {https://doi.org/10.1007/s10958-007-0183-5},
}

@incollection {MM-alro,
    AUTHOR = {Marvan, M.},
     TITLE = {Another look on recursion operators},
 BOOKTITLE = {Differential {G}eometry and {A}pplications},
    SERIES = {Proc. Conf. Brno.},
     PAGES = {393--402},
      NOTE = {\url{https://emis.muni.cz/proceedings/6ICDGA/IV/index.html}},
}

@article {MM-rzcr,
    AUTHOR = {Marvan, M.},
     TITLE = {Reducibility of zero curvature representations with application to
recursion operators},
   JOURNAL = {Acta Appl. Math.},
  FJOURNAL = {Acta Applicandae Mathematicae},
    VOLUME = {83},
      YEAR = {2004},
     PAGES = {39--68},
       DOI = {10.1023/B:ACAP.0000035588.67805.0b},
       URL = {https://doi.org/10.1023/B:ACAP.0000035588.67805.0b},
    EPRINT = {nlin.SI/0306006},
}

@article {MM-spp,
    AUTHOR = {Marvan, M.},
     TITLE = {On the spectral parameter problem},
   JOURNAL = {Acta Appl. Math.},
  FJOURNAL = {Acta Applicandae Mathematicae},
    VOLUME = {109},
      YEAR = {2010},
     PAGES = {239--255},
       DOI = {10.1007/s10440-009-9450-4},
       URL = {https://doi.org/10.1007/s10440-009-9450-4},
    EPRINT = {0804.2031},
}

@incollection {MDTFB-2020,
    AUTHOR = {Montagne, N. and Douthe, C. and Tellier, X. and Fivet, C. and Baverel, O.},
     TITLE = {Voss surfaces: A design space for geodesic gridshells},
 BOOKTITLE = {Inspiring the {N}ext {G}eneration (Proc. IASS Annual Symp. 2020 and 7th Int. Conf. Spatial Structures)},
     PAGES = {3473--3483},
 PUBLISHER = {Spatial Structures Research Centre of the University of Surrey},
      YEAR = {2021},
       DOI = {10.15126/900337},
       URL = {https://doi.org/10.15126/900337},
}

@article {MDTFB-2022,
    AUTHOR = {Montagne, N. and Douthe, C. and Tellier, X. and Fivet, C. and Baverel, O.},
     TITLE = {Discrete {V}oss surfaces: {D}esigning geodesic gridshells with planar cladding panels},
   JOURNAL = {Autom. Constr.},
  FJOURNAL = {Automation in Construction},
    VOLUME = {140},
      YEAR = {2022},
     PAGES = {104200, 19~pages},
       DOI = {10.1016/j.autcon.2022.104200},
       URL = {https://doi.org/10.1016/j.autcon.2022.104200},
}

@article {PJO-1977,
    AUTHOR = {Olver, Peter J.},
     TITLE = {Evolution equations possessing infinitely many symmetries},
   JOURNAL = {J.~Math. Phys.},
  FJOURNAL = {Journal of Mathematical Physics},
    VOLUME = {18},
      YEAR = {1977},
    NUMBER = {6},
     PAGES = {1212--1215},
       DOI = {10.1063/1.523393},
       URL = {https://doi.org/10.1063/1.523393},
}

@article {CJP-1991,
    AUTHOR = {Papachristou, C. J.},
     TITLE = {Lax pair, hidden symmetries, and infinite sequences of
              conserved currents for self-dual {Y}ang--{M}ills fields},
   JOURNAL = {J.~Phys.~A},
  FJOURNAL = {Journal of Physics. A. Mathematical and General},
    VOLUME = {24},
      YEAR = {1991},
    NUMBER = {17},
     PAGES = {L1051--L1055},
       DOI = {10.1088/0305-4470/24/17/015},
       URL = {https://doi.org/10.1088/0305-4470/24/17/015},
}

@mics {AR-2025,
    AUTHOR = {Rasoulzadeh, A.},
     TITLE = {Classification of smooth alignable {V}oss surfaces},
    EPRINT = {2603.17501},
}

@article {AR-1889,
    AUTHOR = {Razzaboni, A.},
     TITLE = {Delle superficie sulle quali due serie di geodetiche formano un sistema
conjugato},
   JOURNAL = {Mem. Acad. Sci. Bologne},
  FJOURNAL = {Memorie della Reale Accademia delle Scienze dell'Istituto di Bologna},
    VOLUME = {9},
      YEAR = {1889},
    NUMBER = {4},
     PAGES = {765--776},
}

@article {R-L-W-2001,
    AUTHOR = {Reid, Gregory J. and Lin, Ping and Wittkopf, Allan D.},
     TITLE = {Differential elimination-completion algorithms for {DAE} and
              {PDAE}},
   JOURNAL = {Stud. Appl. Math.},
  FJOURNAL = {Studies in Applied Mathematics},
    VOLUME = {106},
      YEAR = {2001},
    NUMBER = {1},
     PAGES = {1--45},
       DOI = {10.1111/1467-9590.00159},
       URL = {https://doi.org/10.1111/1467-9590.00159},
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@mics {sammlung,
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@book {VR-2000,
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@article {ES-1924,
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   JOURNAL = {Math.~Z.},
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@book {RS-1970,
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@article {ET-1939,
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@article {VEZ-BGK-1984,
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@article {Z-T-F-1974,
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@article {Z-1994,
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}
