Christof Thoenes studied art history in Berlin and Pavia, before completing his doctorate in Berlin. Thoenes lives in Rome, where for many years he has worked for the Bibliotheca Hertziana (Max-Planck-Institute), and is honorary professor in Hamburg. He has contributed to numerous publications on Italian art, particularly on architecture and architectural theory of the 15th to 18th centuries. Frank Zollner wrote his doctoral theses on artistic and architectural theory (1987) and Leonardo da Vinci (1996). He has written numerous publications on the art and artistic theory of the Renaissance and on Paul Klee. Since 1996 he has been Professor of Renaissance and Modern Art at Leipzig University. He is also the author of TASCHEN's XI monograph on Leonardo da Vinci. Thomas Popper wrote his doctoral theses on 15th century Italian Renaissance sculpture. He has been a fellow of the Bibliotheca Hertziana (Rome) and has worked as a curator for contemporary art at the Schleswig-Holsteinisches Landesmuseum. He taught at the Northern Institute of Technology and at the University of Hamburg. Since 2005 he has been a lecture of art history at Leipzig University. Popper is the author of a range of publications on Italian Medieval, Renaissance, and Baroque art as well as on 19th and 20th century German painting and sculpture.