\ifx\undefined\bysame

\newcommand{\bysame}{\leavevmode\hbox to3em{\hrulefill}\,}

\fi

\begin{thebibliography}{1}



\bibitem{GelZakh89Spe}

I.~M. Gelfand and I.~S. Zakharevich, {\em Spectral theory of a pencil of

  third-order skew-symmetric differential operators on $s\sp 1$}, Functional

  Analysis and its Applications {\bf 23} (1989), no.~2, 85--93.



\bibitem{GelZakh91Web}

\bysame, {\em Webs, {V}eronese curves, and bi-{H}amiltonian systems}, Journal

  of Functional Analysis {\bf 99} (1991), no.~1, 150--178.



\bibitem{GelZakhMSRI}

Israel~M. Gelfand and Ilya Zakharevich, {\em The spectral theory for a pencil

  of skew-symmetrical differential operators of third order}, preprint

  MSRI-06627-91, MSRI, Berkeley, CA, 94720, 1991.



\bibitem{GonPC}

Alexander Goncharov, private communication, 1990.



\bibitem{Kod}

Kunihiko Kodaira, {\em Complex manifolds and deformation of complex

  structures}, Grundlehren der mathematischen Wissenschaften, vol. 283,

  Springer-Verlag, New York, 1986.



\bibitem{Mag}

F.~Magri, {\em Geometry and soliton equations}, La M\'ecanique Analytique de

  Lagrange et son h\'eritage, Coll\`ege de France, September 1988.



\bibitem{McKeanPC}

Henri McKean, private communication, 1990.



\bibitem{Tur89Cla}

Francisco-Javier Turiel, {\em Classification locale d'un couple de formes

  symplectiques {P}oisson-compatibles}, Comptes Rendus des Seances de

  l'Academie des Sciences. Serie I. Mathematique {\bf 308} (1989), no.~20,

  575--578.



\bibitem{Wei83Loc}

Alan Weinstein, {\em The local structure of {P}oisson manifolds}, J.

  Differential Geom. {\bf 18} (1983), no.~3, 523--557.



\end{thebibliography}