A Matrix Example

Kiers \cite{kiers} considers the problem of minimizing a function of the form $$\phi(X)=c+\text{tr }AX + \sum_{j=1}^m\text{tr }B_jXC_jX',$$ over all $n\times p$ matrices $X,$ possibly with restrictions. He shows that this covers a large number of matrrix problems commonly considered in psychometrics.