2022-05-122022-05-121963https://hdl.handle.net/2152.3/11443One stamp from Poland, Paraguay, Ghana, United States, two from Israel, and six from Zaire featuring Albert Einstein. Two stamps from Denmark featuring Niels Bohr. One stamp of Einstein's equation from Nicaragua.Fifteen stamps.Stamp collectingPostage-stamp albumsEinstein, Albert, 1879-1955Bohr, Niels, 1855-1962PolandParaguayDenmarkNicaraguaIsraelMathematicsMassEnergyZaire