Porter, Vincent (2000). "The Robert Clark Account". Historical Journal of Film, Radio and Television. 20 (4): 495. doi:10.1080/713669742. S2CID161670089.
Porter, Vincent (2000). "The Robert Clark Account". Historical Journal of Film, Radio and Television. 20 (4): 495. doi:10.1080/713669742. S2CID161670089.