Mackensen, Ludolf von <br/><br/>
German natural scientists and inventors over four centuries / 
Ludolf von Mackensen ; with contributions by Volker Bialas ... (et al.) 
 - Bonn :  Inter Nationes,  1991 
 - 61 p. :  ill. ;  20 cm. 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Naturalists--Germany<br/>Scientists--Germany