The images (so far) are from the beginning plates of Durand's Precis and the 1975 a+u issue featuring the work of Hejduk. I was surprised by the similarity of the first plans featured in both publications:
[Texas] House 1
From there, images/details were chosen from following pages of each publication more or less in subsequent order, although more strictly following Durand than Hejduk. Mind you, only the thinnest layer of surface has been scratched in terms of Hejduk images available.
Regarding the 'elegance' of the images combined, I suspect the elegance is already within the images separately, and their combination is then fortunately synergistic. The 'collages' were generated by using one author's image as a "paint fill" applied to the other author's image--the results are more happy accidents than planned/intended outcomes. The same 'image paint fill' operation was often utilized throughout the generation of 2001's Quaestio Abstrusa Backgrounds.