2022-03-152022-03-151971https://hdl.handle.net/2152.3/11378"Pythagorias' Law" 30c. air stamp depicting the Pythagorean theorem on the Parthenon. "Boltzmann's Law" 40c. air stamp depicting "the application of petroleum gases within cylinders and the resultant explosive forces driving simple cranks."Two stamps from The Ten Mathematical Equations that Changed the Face of the Earth series. Issued by Nicaragua on May 15, 1971.Stamp collectingPostage-stamp albumsNicaraguaGeometry in architecturePythagorean theoremPythagorasBoltzmann, Ludwig, 1844-1906Combustion