British Rail Train-Crew Manual - Class 56 -  Drivers Fault Finding Data.
Issue Date: March 1980   -   BR 33056/67  Issue 1.


More information can be found here Wikipedia - British Rail Class 56 
More Information Regarding Preserved Class 58 Locomotives can be found on the following websites:  Preserved - Diesels - Class 56  -  The Class 56 Group