The *Bilinear Operator* is composite operator that is
often used in missing data estimations at SEP.
Furthermore, the Hessian of a vector valued function is a
Bilinear Operator (see jam paper). All second order
tensors are bilinear operators.
A Bilinear Operator is an operator that is
linear with respect to when is constant,
and vice versa.
A convolution is a bilinear operator with respect to its
filter coefficients and its input data.
Bilinear operators are better behaved then fully non-linear
operators, e.g., their gradient is easily computed.

3/8/1999