Question about Mackay's Appendix A

In Appendix A of Ron Mackay's Ridgewell's Flying Fortressess there are some acronyms that I don't understand and there seems to be no explanation. Under the Whaletail II it has the following: See BELB 32, FREH 126, MACA 34, MACB 12, MACD 22, NASA 4201AC, SCUC16

Can anyone offer an explanation as to what any of this is referring to? Thanks Chip

Chip -
These are Photo references.
Books and Periodicals: Numbers are Page #
BELB - Air Force Colors Vol. II ETO , MTO by Dana Bell
FREH -  B - 17 Fortress At War by Roger Freeman
MACA -  Triumphant We Fly  Part I: 381st BG in WW II 
              Combat Report Vol. I #3 by Ron Mackay 
MACB -  Triumphant We Fly Part II : Combat Report Vol. I #4
MACD - The 381st Bomb Group by Ron Mackay
SCUC -   B - 17 Flying Fortress by Jerry Scutts
----------------------------------------------------------
NASA -  National Air and Space Museum Library
             PHOTO # 4201AC
Cheers,
Mike