  We discuss the differing definitions of complex and quaternionic projective
group representations employed by us and by Emch. The definition of Emch
(termed here a strong projective representation) is too restrictive to
accommodate quaternionic Hilbert space embeddings of complex projective
representations. Our definition (termed here a weak projective representation)
encompasses such embeddings, and leads to a detailed theory of quaternionic, as
well as complex, projective group representations.
