His encyclopedic book in spectral graph theory, Spectra of Graphs. Theory and Applications (with Dragos Cvetković and Michael Doob) has several editions and was translated in several languages.[4][5][6][7][8][9]
Two theorems in graph theory bear his name. One of them relates the coefficients of the characteristic polynomial of a graph to certain structural features of the graph. Another one is a simple relation between the characteristic polynomials of a graph and its line graph. Sachs subgraphs are also named after Sachs.