Sobolev inner products and orthogonal polynomials of Sobolev type

This survey paper deals with polynomials which are orthogonal with respect to scalar products of the form _R F ^TA]G withF ^T=f(x), f(Ⅎ(x),...f ^(y)(x)], A] A _ji =A _ji =A _ij =d _ji (I _ji ) where d _ji is a measure of supportI _ij and A] is positive semi-definite. Basic properties are indicated or proved in particular cases.