How did Taimanov lose this game to Karpov? I can't understand how Taimanov (playing White) resigned in the following position against Karpov from the Moscow team leagues in 1973:



After 40.Rc2 or 40.d5 the position seems to be equal. I know Taimanov was notorious for getting into time trouble. Did he just forfeit on time?
In the book "How Karpov Wins" by Edmar Mednis it is stated on page 174 that "White overstepped the time limit and lost". The book seems to be fully available on Google books and has a lot more analysis of the match.

https://books.google.com.au/books?id=x8MV0uoAJp0C