Appears in collection : Conférence à la mémoire de Vadim Knizhnik

There are two natural ways to constract the new vertex algebras.One -as subalgebra in the known one.Bosonisation is the special case of this construction.The second idea is opposite -to get the new algebras as exstensions ,in this case we add to vertex algebra some combination of vertex operators.We discuss several examples .Some of them are related with AGT bisiness.