J. Vasundhara Devi, S.Srinivasa Rao, and I.S.N.R.G.Bharat. 2015. “Periodic Boundary Value Problem for the Graph Differential Equation and the Matrix Differential Equation”. Malaya Journal of Matematik 3 (04). India:598-606. https://doi.org/10.26637/mjm304/018.