"- KEIL C, any 8031 compatible C,
- 8031 ASM,
- Hardware and software of 8031 family,"

All here!

For Keil-specific discussion, see their forum at www.keil.com


"- PC (all type connections to microcontroler
(RS232,RS485, Paralel port), drivers (on PC)
for this connections or tehnical data about
them)."

http://www.epanorama.net/index.php
http://msdn.microsoft.com/

"Can you recommend me any books about 8031 family"

See the 'Books' page on this site.

There is also a bibliography on the Keil site