[986] Approximation of Sobolev functions in Jordan domains

[987] Some problems of diophantine approximation

[988] The congruence$ax$^{3}+by^{3}+c≡0 (mod$xy$), and integer solutions of cubic equations in three variables

[989] A non-harmonic fourier series

[990] A cutting and pasting of noncompact polygons with applications to fuchsian groups