Example sentences of "have been known since [art] " in BNC.
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1 | In fact it has been known since the late 1950s ( see for example Nature , vol. 208 , p 423 ) that Po is widely distributed in the environment , and in man , as a result of atmospheric fall-out of the decay products of natural radon-222 , with an abundance in northern temperate latitudes of about 0.06 curie per sq.km or of the order of 10 6 curies in total over the surface of the world land mass . |
2 | It has been known since the 1970s that the vehicles which have dramatically increased our mobility in the last 50 years have also constituted a grave danger . |
3 | The site , near modern Kerma , has been known since the 1920s but the city underneath has only emerged over the last ten years . |
4 | One in the British Museum ( fig. 77 ) has been known since the eighteenth century and is called the Choiseul-Gouffier Apollo after a former owner . |
5 | He pursued the antimicrobial properties of soil organisms , particularly actinomycetes , which had been known since the 1920s to produce inhibitory substances . |
6 | Mass strandings have been known since the time of the ancient Greeks ; Aristotle himself recorded them . |