2022-03-152022-03-151971https://hdl.handle.net/2152.3/11379"De Broglie's Law" 1cor. air stamp depicting "diffraction circles made by an electron microscope." "Archimedes' Law" 2cor. air stamp depicting "a pair of scales and a foundry scene of molten metal being poured from a ladle into a mould."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 albumsNicaraguaBroglie, Louis de, 1892-1987Electron microscopeArchimedesArchimedes' principle