British Railways Driver's Manual - Class 56 -  Preparation and Disposal Instructions for Class 56 Locomotives.
Issue Date: February 1977   -   BR 33056/56 Issue 1.


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