Department of Mathematical Sciences;
Norwegian University of Science and Technology;
NO–7491 Trondheim;
Norway;
Centre of Mathematics for Applications;
University of Oslo;
P.O. Box 1053;
Blindern;
NO–0316 Oslo;
Norway;
Centre of Mathematics for Applications;
University of Oslo;
P.O. Box 1053;
Blindern;
N–0316 Oslo;
Norway;
Faculty of Mathematics;
University of Montenegro;
81000 Podgorica;
Montenegro;
Mathematical Analysis Department;
Novgorod State University;
ul. B. St. Peterburgskaya 41;
173003 Veliky Novgorod;
Russia;
非退化; 函数方程; 通量; 椭圆; 近似解; 双曲线; 压实度; 间断;