2022-04-282022-04-281971https://hdl.handle.net/2152.3/11415One 1951 50 ore stamp of Hans Øersted from Denmark. One 25dm stamp of Hermann von Helmhotz from Germany. One stamp of André Ampère. Three stamps of Heinrich Hertz from Germany, Czechoslovakia, and Mexico. One 10dm stamp from Germany, one 1Kcs stamp from Czechoslovakia, and one 1967 80¢ stamp from Mexico. One Nicaragua stamp featuring the Ten Mathematical Equations.Seven Stamps.Postage-stamp albumsStamp collectingØrsted, Hans Chirstian, 1777-1851Helmholtz, Hermann von, 1821-1894Hertz, Heinrich, 1857-1894ElectricityDenmarkGermanyNicaraguaMexicoCzechoslovakiaAmpère, André-Marie, 1775-1836