The vertical lines connect students (above) with their advisors (below).
This information was taken from the Mathematics Genealogy Project.

 

Pantelimon Stanica State University of New York at Buffalo & Institute of Mathematics of Romanian Academy 1998

Thomas W. Cusick Cambridge 1968 Nicolae Popescu Bucharest 1967   Harold Davenport Cambridge, 1938     John Littlewood Cambridge 1907     Ernest Williams Barnes Walter William Rouse Ball