(1991). Arbitrary powers of D'alembertians and the huygengs' principle. [s.l.]: [s.n.].
1991. Arbitrary powers of D'alembertians and the huygengs' principle. [s.l.]: [s.n.].
Arbitrary powers of D'alembertians and the huygengs' principle. [s.l.]: [s.n.]. 1991.