V. Tomno, F. Nyamwala, and W. Kamaku, “The Wss P0 Matrix Completion Problem for Symmetric Patterns of Acyclic Digraphs of Order Four”, IJSBAR, vol. 37, no. 1, pp. 112–121, Jan. 2018, Accessed: Oct. 12, 2025. [Online]. Available: https://www.gssrr.org/JournalOfBasicAndApplied/article/view/8591