Probabilities of opponents hands after flops

[richrf]

Hi,

I have been experimenting with Texas Calculatum, and I have noticed that the odds that an opponent, in say a 10 player game, of catching a hand (flush, full house, straight, etc.) are much higher than I had originally thought. Is there a book, article, or software that can help me better understand the probabilities that an opponent will have a given hand after a flop. Thanks.

Rich