then I wondered why the string was so important

Browsing the aforementioned magazine, I was overwhelmed by many memories.
First, we mention the then student Gheorghe SILBERBERG and the solution to problem No. 4 from OIM (page 432).

It's a joke, but the question has been asked. Also the answer.

His PhD thesis in Mathematical Sciences is inaccessible to the public.

The magazine in the first image contains an article (at pages 1-4) with the theme mentioned in the title. In the second image is an access code to the works mentioned by me in the post.

The article is incorrect and incomplete, each of you can judge for yourself.

Gheorghe VRĂNCEANU, Lecții de Geometrie Diferențială, Editura Didactică și Pedagogică, București; vol 1 (1976), 2 (1977), 3 (1979)

Click on the year of publication of the book (the few exceptions have the indication "f.a." - that is, without year)

Să mă prezint. Dacă sunteți curioși de ce fac videoclipuri despre călătoriile mele, avantajele și dezavantajele vieții de nomad și de ce să nu deveniți un vloggler, urmăriți acest vlog!