The solution to the mystery of how A. I. Petrov wrote a paper in 1964, when he was a student writing what appears to be his first paper in 1971, is that mathnet.ru has mistakenly taken his name to be A. I. Petrov, when in fact he is A. I. Perov, as you can see in the Wronskian paper. Moreover, Perov is still working at Voronezh State University, and I can send you his email address if you contact me at [email protected]. I don't know if he will help you, but the paper was part of a special collection of abstracts, so was not translated in the usual Doklady translations into English. The paper is pretty clearly translated using DeepL, so I don't think you really need a German or English reference.

The solution to the mystery of how A. I. Petrov wrote a paper in 1964, when he was a student writing what appears to be his first paper in 1971, is that mathnet.ru has mistakenly taken his name to be A. I. Petrov, when in fact he is A. I. Perov, as you can see in the Wronskian paper. Moreover, Perov is still working at Voronezh State University, and I can send you his email address if you contact me at [email protected]. I don't know if he will help you, but the paper was part of a special collection of abstracts, so was not translated in the usual Uspekhi translations into English. The paper is pretty clearly translated using DeepL, so I don't think you really need a German or English reference.