On some special surfaces connected with convex surfaces of the Lobachevskij space. Ionin, V.K. — 2002 Sibirskij Matematicheskij Zhurnal
Closed geodesics in simply connected Riemannian spaces of negative curvature. Ionin, V.K. — 2000 Siberian Mathematical Journal
Inequalities between the radii of spheres that are connected with a convex surface in a space of constant curvature. Ionin, V.K. — 2001 Sibirskij Matematicheskij Zhurnal
Two special simply connected spaces of nonpositive curvature. Ionin, V.K. — 2003 Sibirskij Matematicheskij Zhurnal