V. A. Nersesian, “POSSIBLE COMPLEXES OF THREE-DIMENSIONAL PLANES IN PROJECTIVE SPACE  P6. II”, Proc. YSU A: Phys. Math. Sci., vol. 36, no. 1 (197), pp. 34–38, Mar. 2002, doi: 10.46991/PYSUA.2002.36.1.034.