A classical theorem of Stafford says: every left ideal of partial different
ial operators with rational or even polynomial coefficients inn variables c
an be generated by two elements. The highly involved proof of this theorem
is reorganized and completed for rational coefficients in order to yield a
procedure which guarantees the computability in finitely many steps. Conseq
uences for an eventual normal form for matrices of such operators are discu
ssed. (C) 2001 Academic Press.