00299nam a2200097Ia 4500008004100000082001600041100003100057245006700088260003800155300000800193140113s9999    xx            000 0 und d  a631.84   L7  a"Ayanaba, A. & Dart, P.J."  aBiological Nitrogen fixation in farming systems of the tropics  a1977bJohn Wiley & SonscNew York  a377