@incollection{TeschlUnterkofler2013, author = {Gerald Teschl and Karl Unterkofler}, title = {Spectral theory as influenced by Fritz Gesztesy}, series = {Spectral analysis, differential equations and mathematical physics. A festschrift in honor of Fritz Gesztesy's 60th birthday}, editor = {Helge Holden and Barry Simon and Gerald Teschl}, publisher = {American Mathematical Society}, address = {Providence, RI}, doi = {10.1090/pspum/087}, pages = {341 -- 364}, year = {2013}, language = {en} }