In 1972 the government of the People's Republic of China donated two giant pandas to the zoo after President Richard Nixon's historic trip to China.
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... is covered by US patents 3,726,146 (1973) and 5,353,655 (1994) by L.A. Mishler and US patent 5,800,311 (1998) by P.S.Chuang. External links www.gyrotwister.de ...