Brown, Emily C., Har Dayal, Hindu Revolutionary and Rationalist (Tucson: University of Arizona Press, 1975)
Dharmavira, Lala Har Dayal and Revolutionary Movements of his Times (New Delhi: Indian Book Company, 1970)
Dharmavira (ed.), Letters of Lala Har Dayal (Ambala Cantt.: Indian Book Agency, 1970).
Gould, Harold A., Sikhs, Swamis, Students and Spies: The India Lobby in the United States, 1900-1946 (New Delhi: Sage, 2006)
Kapila, Shruti, Har Dayal: Terror and Territory (Delhi: Routledge, 2009)
Paul, E. Jaiwant & Paul, Shubh, Har Dayal: The Great Revolutionary (New Delhi: Lotus Collection, 2003)