Tomno, Victor, Fredrick Nyamwala, and Waweru Kamaku. “The Wss P0 Matrix Completion Problem for Symmetric Patterns of Acyclic Digraphs of Order Four”. International Journal of Sciences: Basic and Applied Research (IJSBAR) 37, no. 1 (January 15, 2018): 112–121. Accessed October 12, 2025. https://www.gssrr.org/JournalOfBasicAndApplied/article/view/8591.