2020-03-27 0 0 0 Nicaragua 1971 Mi 1615 stamp and back (The Ten Mathematical Equations that Changed the Face of the Earth. Einstein's theory - relativity).jpg
2021-02-01 0 0 0 Nicaragua 1971 Mi 1614 stamp and back (The Ten Mathematical Equations that Changed the Face of the Earth. Newton's law - gravity).jpg
2021-09-06 0 0 0 Nicaragua 1971 Mi 1616 stamp and back (The Ten Mathematical Equations that Changed the Face of the Earth. Tsiolkovski's law - speed of rockets).jpg
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