Kim & Rote 2016, p. 6, § 5. Four-Dimensional Rotations. Kim, Heuna; Rote, Günter (2016). "Congruence Testing of Point Sets in 4 Dimensions". arXiv:1603.07269 [cs.CG].
Kim & Rote 2016, pp. 7–10, § 6. Angles between two Planes in 4-Space. Kim, Heuna; Rote, Günter (2016). "Congruence Testing of Point Sets in 4 Dimensions". arXiv:1603.07269 [cs.CG].
Kim & Rote 2016, pp. 8–10, Relations to Clifford Parallelism. Kim, Heuna; Rote, Günter (2016). "Congruence Testing of Point Sets in 4 Dimensions". arXiv:1603.07269 [cs.CG].
Kim & Rote 2016, pp. 7–8, § 6 Angles between two Planes in 4-Space; Left and Right Pairs of Isoclinic Planes. Kim, Heuna; Rote, Günter (2016). "Congruence Testing of Point Sets in 4 Dimensions". arXiv:1603.07269 [cs.CG].