Ten Mathematical Equations 7

Date
1971
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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 "Napier's Law," "Pythagorias' Law," "Boltzmann's Law," "De Broglie's Law," and "Archimedes' Law" stamps.
Keywords
First day covers (Philately), Stamp collecting, Postage-stamp albums, Nicaragua, Air mail envelopes
Citation