Ten Mathematical Equations 6
Abstract
First-day cover with five stamps from The Ten Mathematical Equations that Changed the Face of the Earth series. Issued by Nicaragua on May 15, 1971.
Description
First-day cover featuring "One plus one equals two," "Newton's Law," "Einstein's Law," "Tsiolkovsky's Law," and "Maxwell's Law" stamps.
Keywords
First day covers (Philately), Stamp collecting, Postage-stamp albums, Nicaragua, Air mail envelopes