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1 · Religion and Magic
2 · Nature
3 · Human Being, Man in General
4 · Society, Civilization, Culture
5 · Abstract Ideas and Concepts
6 · History
7 · Bible
8 · Literature
9 · Classical Mythology and Ancient History
Top
4 · Society, Civilization, Culture
49 · education, science and learning
49E · science and technology
49E2 · physics and mechanics
49E25 · optics
49E251 · optical instruments
49E2511 · lens
49E2512 · microscope
49E2513 · binoculars, spy-glass, etc.
49E2514 · telescope