A good reference specific to aircraft specifications is Chapter 8 of the MMPDS. the NASA Structures Manual is another good resource and is available online for free. The MMPDS is not free, but you can find it's predecessor, MIL-HDBK-5 online for free. I think revision J was the last one prior to changing to the MMPDS. A good reference for understanding fastener spacing in aircraft applications is Flabel's Structural Analysis for Design Engineers. Of course, Bruhn and Niu are good references as well, but not quite as accessible as Flabel.
"On the human scale, the laws of Newtonian Physics are non-negotiable"