  This paper, dedicated to the memory of late Professor Tiberiu Constantinescu,
discusses two parametrizations of positive matrices. The first, called the
Schur-Constantinescu parametrization, is used to construct several examples of
separable states (e.g., Hankel states). The second, called the Jacobi
parametrization, is used to present an alternative to the Bloch sphere
representation of qubits.
