His revived interest in research, however, meant that four research papers appeared in the three years 1968-70 written while he worked on his book on Clifford parallelism.
Revived kanyang interes sa pananaliksik, gayunpaman, sinadya na apat na research papers lumitaw sa tatlong taon 1968-70 nakasulat na habang siya ay nagtrabaho sa kanyang mga libro sa Clifford paralelismo.