Haurongo: Butler, Robert
He whakaaturanga anō
Rārangi pukapuka
Carson, W. H. & J. R. Sheehan. The Kaiwarra mystery and more famous trials. Wellington, 1935
Tonkin, L. C. Robert Butler. Dunedin, 1980
Trial of Butler for the Dunedin tragedy. Christchurch, 1880