  We study necessary and sufficient conditions for a dg bimodule to yield
triangle equivalences between (quotients of) the corresponding derived
categories. This is related to recent work by Bazzoni-Mantese-Tonolo, Yang,
Angeleri H\"ugel-Koenig-Liu, Chen-Xi, Bazzoni-Pavarin,... on large tilting
modules, homological epimorphisms and recollements.
