2022-03-082022-03-081971https://hdl.handle.net/2152.3/11375"One plus one equals two" 10c. stamp depicting a "primitive [person] over cerebrum, deducing 1+1=2, the simple equation which formed the basis of counting and which underlies mathematics." "Newton's Law" 15c. stamp depicting "the legend of the falling apple."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 albumsNicaraguaNewton, Isaac, 1642-1727CountingMathematicsGravity