00293nam a2200097Ia 4500008004100000082002400041100001700065245008300082260002300165300000700188140113s9999    xx            000 0 und d  a631.527.52:635   H6  a"Ashton, T."  aThe Use of heterosis in the production of agricultural and horticultural crops  a1949bCABcFarnham  a30