See the writings and speeches of Oliver Cromwell (ed. by W. C. Abbott et al., 4 vol., 1937–47); biographies by M. P. Ashley (1969), J. E. C. Hill (1970), C. V. Wedgwood (rev. ed. 1973), and A. Fraser (1973); M. P. Ashley, The Greatness of Oliver Cromwell (1957, repr. 1966); writings on the period by S. R. Gardiner and Sir Charles Firth.