Separating Bulgarian And Russian

Are there any workable rules for separating Bulgarian and Russian stamps. I will eventually be looking up each of the stamps but at this stage I would like to separate these two countries from each other just so I am not constantly looking in the Russian area for a stamp that ends up being Bulgarian, etc. I know this may still occur with a few but I don't want it to occur unnecessarily. I'm pretty sure that NOWA does not help in this sort but of course CCCP is Russian. Any rules like that would help immensely. Stamps being sorted are potentially of any years. Thanks, Jim

This might help a little.

http://www.thestampcollector.net/wwidcyrillic.html

http://www.philatelicdatabase.com/p...ry/bulgaria/