Contents

Vestnik St. Petersburg University, Mathematics

Vol. 53, No. 2, 2020

Ramanujan Denesting Formulas for Cubic Radicals

M. A. Antipov and K. I. Pimenov p. 115  abstract

Automorphisms of Finite Quasi-Groups without Sub-Quasi-Groups

V. A. Artamonov p. 122  abstract

Calculations in the Generalized Lubin–Tate Theory

S. V. Vostokov and E. O. Leonova p. 131  abstract

Linear Operators Preserving Majorization of Matrix Tuples

A. E. Guterman and P. M. Shteyner p. 136  abstract

On Sufficient Conditions for the Closure of an Elementary Net

A. K. Gutnova and V. A. Koibaev p. 145  abstract

Homological Properties of Quotient Divisible Abelian Groups and Compact Groups Dual to Them

N. I. Kryuchkov p. 149  abstract

Hazewinkel Functional Lemma and Classification of Formal Groups

A. I. Madunts p. 155  abstract

Supercharacter Theory for the Borel Contraction of the Group GL(n, ${{\mathbb{F}}_{q}}$)

A. N. Panov p. 162  abstract

On the Stability of the Nonlinear Center under Quasi-periodic Perturbations

V. V. Basov and Yu. N. Bibikov p. 174  abstract

On the Existence of a Solution to the Cauchy Initial Boundary Value Problem

V. V. Basov and Yu. A. Iljin p. 180  abstract

On Problems of Stability Theory for Weakly Hyperbolic Invariant Sets

N. A. Begun p. 191  abstract

The Stability of Periodic Solutions of Periodic Systems of Differential Equations with a Heteroclinic Contour

E. V. Vasil’eva p. 197  abstract

On the Aizerman Problem: Coefficient Conditions for the Existence of Three- and Six-Period Cycles in a Second-Order Discrete-Time System

T. E. Zvyagintseva p. 206  abstract

Qualitative Studies of Some Biochemical Models

C. Pantea and V. G. Romanovski p. 214  abstract

Mathematics

Constructing c-Optimal Designs for Polynomial Regression without an Intercept

V. B. Melas and P. V. Shpilev p. 223  abstract

Second Order Monotone Difference Schemes with Approximation on Non-Uniform Grids for Two-Dimensional Quasilinear Parabolic Convection-Diffusion Equations

Le M. Hieu, Dang N. H. Thanh and V. B. Surya Prasath p. 232  abstract

Errata

Erratum to: Generalized Semicommutative Rings

Debraj Roy and Tikaram Subedi p. 241  abstract