1. Campbell, S.L.: Singular systems of differential equations I, (Pitman, London 1980)
2. Campbell, S.L.: Singular systems of differential equations II, (Pitman, London 1982)
3. Wilkinson, J.H.: ‘Note on the practical significance of the Drazin inverse’, Campbell, S.L., Recent applications of generalised inverses, (Pitman, London 1982)