Bulgaria Olympics Stamps

I have 4 Bulgarian stamps issued for the 1984 Olympics. They have catalog numbers in Michel but no Scott numbers. Anybody know the reason why?

This issue is mentioned in SG catalogues. A number of sets issued in 1983 were not available to the public at face value so are not given full listing, only a mention.
This probably the reason why Scott don't list them.
Michel list them all. As a Bulgaria Collector, I have noticed many issues, especially Miniature Sheets, that are not in Scott or Gibbons but are listed in Michel.
A total of 4 sets of Bulgaria stamps were issued in 1983 with 'restricted distribution' !

Londonbus1

Thanks for the info LB. I thought perhaps it had something to do with the Eastern Bloc nations boycotting the Olympics in Los Angeles. But your explanation makes more sense.