Various modern historians writing on Shaka and the Zulu point to the uncertain nature of Fynn and Isaac's accounts of Shaka's reign. A standard general reference work in the field is Donald Morris's "The Washing of The Spears", which notes that the sources, as a whole, for this historical era are not the best. Morris nevertheless references a large number of sources, including Stuart, and A. T. Bryant's extensive but uneven "Olden Times in Zululand and Natal", which is based on four decades of exhaustive interviews of tribal sources. After sifting through these sources and noting their strengths and weaknesses, Morris generally credits Shaka with a large number of military and social innovations, and this is the general consensus in the field.