Geroch, R.; Held, A.; Penrose, Roger A space-time calculus based on pairs of null directions. (English) Zbl 0875.53014 J. Math. Phys. 14, No. 7, 874-881 (1973). MSC: 53Z05 83C05 83C60 PDFBibTeX XMLCite \textit{R. Geroch} et al., J. Math. Phys. 14, 874--881 (1973; Zbl 0875.53014) Full Text: DOI
Geroch, R.; Kronheimer, E. H.; Penrose, Roger Ideal points in space-time. (English) Zbl 0257.53059 Proc. R. Soc. Lond., Ser. A 327, 545-567 (1972). MSC: 53C50 PDFBibTeX XMLCite \textit{R. Geroch} et al., Proc. R. Soc. Lond., Ser. A 327, 545--567 (1972; Zbl 0257.53059) Full Text: DOI