Collecting: Literature

Philatelic literature is written material relating to philately, primarily information about postage stamps and postal history. Philatelic literature is held by stamp collectors and dealers, philatelic societies, and general and specialist libraries. Philatelic literature is generally divided into the following categories: Auction catalogues Books Bibliographies of philatelic literature Background material…

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Thematic: Petroleum

Petroleum is a naturally occurring, yellowish-black liquid found in geological formations beneath the Earth’s surface. It is commonly refined into various types of fuels. Components of petroleum are separated using a technique called fractional distillation, i.e. separation of a liquid mixture into fractions differing in boiling point by means of…

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