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C.~Araujo and J.~Koll{\'a}r.
\newblock Rational curves on varieties.
\newblock In K.~J. B\"or\"oczky, J.~Koll\'ar, and Szamuely T., editors, {\em
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A.~Beauville, J.-P. Bourguignon, and M.~Demazure, editors.
\newblock {\em G\'eom\'etrie des surfaces {$K3$}: modules et p\'eriodes}.
\newblock Soci\'et\'e Math\'ematique de France, Paris, 1985.
\newblock Papers from the seminar held in Palaiseau, October 1981--January
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F.~A. Bogomolov and Yu. Tschinkel.
\newblock Density of rational points on {E}nriques surfaces.
\newblock {\em Math. Res. Lett.}, 5(5):623--628, 1998.

\bibitem{bt}
F.~A. Bogomolov and Yu. Tschinkel.
\newblock Density of rational points on elliptic {$K3$} surfaces.
\newblock {\em Asian J. Math.}, 4(2):351--368, 2000.

\bibitem{Cl}
Herbert Clemens.
\newblock Homological equivalence modulo algebraic equivalence is not finitely
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\newblock {\em Inst. Hautes \'Etudes Sci. Publ. Math.}, (58):19--38, 1983.

\bibitem{Dol}
I.~V. Dolgachev.
\newblock Mirror symmetry for lattice polarized {$K3$} surfaces.
\newblock {\em J. Math. Sci.}, 81(3):2599--2630, 1996.
\newblock Algebraic geometry, 4.

\bibitem{GHS}
T.~Graber, J.~Harris, and J.~Starr.
\newblock Families of rationally connected varieties.
\newblock {\em J. Amer. Math. Soc.}, 16(1):57--67, 2003.

\bibitem{HarTs}
J.~Harris and Yu. Tschinkel.
\newblock Rational points on quartics.
\newblock {\em Duke Math. J.}, 104(3):477--500, 2000.

\bibitem{Hart}
R.~Hartshorne.
\newblock {\em Algebraic geometry}.
\newblock Springer-Verlag, New York, 1977.
\newblock Graduate Texts in Mathematics, No. 52.

\bibitem{h}
B.~Hassett.
\newblock Potential density of rational points on algebraic varieties.
\newblock In {\em Higher dimensional varieties and rational points (Budapest,
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  Berlin, 2003.

\bibitem{HT}
B.~Hassett and Y.~Tschinkel.
\newblock Weak approximation over function fields, 2004.
\newblock preprint, to appear in {\em Inventiones mathematicae}.

\bibitem{kawamata}
Y.~Kawamata.
\newblock On deformations of compactifiable complex manifolds.
\newblock {\em Math. Ann.}, 235(3):247--265, 1978.

\bibitem{LP}
Eduard Looijenga and Chris Peters.
\newblock Torelli theorems for {K}\"ahler {$K3$} surfaces.
\newblock {\em Compositio Math.}, 42(2):145--186, 1980/81.

\bibitem{Mat}
H.~Matsumura.
\newblock {\em Commutative algebra}.
\newblock W. A. Benjamin, Inc., New York, 1970.

\bibitem{Mukai}
S.~Mukai.
\newblock Curves, {$K3$} surfaces and {F}ano {$3$}-folds of genus {$\leq 10$}.
\newblock In {\em Algebraic geometry and commutative algebra, Vol.\ I}, pages
  357--377. Kinokuniya, Tokyo, 1988.

\bibitem{Nik1}
V.~V. Nikulin.
\newblock Finite groups of automorphisms of {K}\"ahlerian {$K3$} surfaces.
\newblock {\em Trudy Moskov. Mat. Obshch.}, 38:75--137, 1979.
\newblock (English translation: Transactions of the {M}oscow {M}athematical
  {S}ociety, 1980, {I}ssue 2, 71--135, American Mathematical Society).

\bibitem{Nik2}
V.~V. Nikulin.
\newblock Integer symmetric bilinear forms and some of their geometric
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\newblock {\em Izv. Akad. Nauk SSSR Ser. Mat.}, 43(1):111--177, 238, 1979.
\newblock (English translation: Math USSR-Izv. 14, no. 1, 103--167 (1980)).

\bibitem{SD}
B.~Saint-Donat.
\newblock Projective models of {$K3$} surfaces.
\newblock {\em Amer. J. Math.}, 96:602--639, 1974.

\end{thebibliography}