What are some professional games where the losing side did not resign before receiving mate?
And how sure are people of the record? In old books they did not care much for complete historical accuracy, so a reference that makes the mate story believable would be better.
Quite a few games here. There are many games with top players that ended in mate.
Most of the games that end in checkmate are where the weak side allows checkmate for whatever reason (he thinks it's a nice win / checkmate, to ruin the publishability of the game, etc), but the strongest example I can think of where a player allowed mate on the board accidentally is Deep Fritz vs Kramnik: http://www.chessgames.com/perl/chessgame?gid=1440796
