With
another piece of research, this time on quantum transport theory
(analyzing aspects of the divergence of density series expansions in
transport theory beyond the dilute Boltzmann gas theory — focusing
on self-diffusion) he obtained the Ph. D. in Physics from the ULB in
January 1970. At that time, a Ph. D. obtained in a foreign university
was not legally accepted in the Spanish university system and many
others like himwere forced to obtain two Ph. D. For his research Manuel
received guidance, besides Prof.