Complex sentence: Another subject with strong mutual influence is projective geometry, where invariant theory can be used to organize the subject, and during the 1960s, new life was breathed into the subject by David Mumford in the form of his geometric invariant theory.
Split into simpler sentences: Another subject with strong mutual influence is projective geometry, where invariant theory can be used to organize the subject. During the 1960s, new life was breathed into the subject by David Mumford in the form of his geometric invariant theory.