This is an interesting article written very clearly and accurqately. The only defect that I found, was reference to equations 1 and 2 instead of (1) and (2) at the beginning. (Editor-in-Chief: FIXED NOW).
Some remarks on the future development, mainly due to Khazin and Shnol, might be included. The reason is that they are not included in the article about Lyapunov Stability.
The paper may be both accepted in its present form, or extended, due to the coise of the author, Professor Shnol'.