Eves 1990, p. 405 Eves, Howard (1990), An introduction to the history of mathematics (6 ed.), Saunders College Publishing, ISBN0-03-029558-0, MR1104435
Eves 1990, p. 494 Eves, Howard (1990), An introduction to the history of mathematics (6 ed.), Saunders College Publishing, ISBN0-03-029558-0, MR1104435
Cajori 1993, Vol. II, p. 92, no. 462 Cajori, Florian (1993), A history of mathematical notations: Including Vol. I. Notations in elementary mathematics; Vol. II. Notations mainly in higher mathematics, Reprint of the 1928 and 1929 originals, Dover, ISBN0-486-67766-4, MR3363427
Camarero, Cristóbal (2018-12-05). "Simple, Fast and Practicable Algorithms for Cholesky, LU and QR Decomposition Using Fast Rectangular Matrix Multiplication". arXiv:1812.02056 [cs.NA].
A proof can be found in the Appendix B of Kondratyuk, L. A.; Krivoruchenko, M. I. (1992). "Superconducting quark matter in SU(2) color group". Zeitschrift für Physik A. 344 (1): 99–115. Bibcode:1992ZPhyA.344...99K. doi:10.1007/BF01291027. S2CID120467300.
A proof can be found in the Appendix B of Kondratyuk, L. A.; Krivoruchenko, M. I. (1992). "Superconducting quark matter in SU(2) color group". Zeitschrift für Physik A. 344 (1): 99–115. Bibcode:1992ZPhyA.344...99K. doi:10.1007/BF01291027. S2CID120467300.
A proof can be found in the Appendix B of Kondratyuk, L. A.; Krivoruchenko, M. I. (1992). "Superconducting quark matter in SU(2) color group". Zeitschrift für Physik A. 344 (1): 99–115. Bibcode:1992ZPhyA.344...99K. doi:10.1007/BF01291027. S2CID120467300.