Subject
- Postage stamps187
- Commemorative postage stamps180
- Science on postage stamps172
- Nobel Prize winners54
- Postmarks54
- Cachets (Philately)52
- Chemists47
- First day covers (Philately)47
- Physicists38
- Women in science18
- Women Nobel Prize winners16
- Physicians15
- Curie, Marie, 1867-193414
- Einstein, Albert, 1879-195514
- Medicine, Persian13
- Muslim scholars13
- Philosophers13
- Alchemists12
- Avicenna, 980-103712
- Congresses and conventions12