British Rail Train Crew Manual - Type 1 D9500 (Later Class 14) Locomotives With Paxman Engine, Voith Transmission Hunslet Final Drive.
Chief Mechanical And Electrical Engineer  Paddington - Issue Date  November 1964   -   BR 33057/11

More information can be found here Wikipedia - British Rail Class 31
More Information Regarding Preserved Class 35s (Hymeks) Locomotives can be found on the following websites:  Preserved-Diesels