  We describe an abstract version of the Theorem of Bogomolov-Tian-Todorov,
whose underlying idea is already contained in various papers by Bandiera,
Fiorenza, Iacono, Manetti. More explicitly, we prove an algebraic criterion for
a differential graded Lie algebras to be homotopy abelian. Then, we collect
together many examples and applications in deformation theory and other
settings.
