NCSC-TG-007: A Guide to Understanding Design Documentation in Trusted Systems, 6 October 1988. (Burgundy Book)
You can download it from the following link: https://packetstormsecurity.com/files/download/13998/NCSC-TG-007.txt
Source: https://packetstormsecurity.com/files/13998/NCSC-TG-007.txt.html