Book excerpt: Papers on Non-Solvable Spaces of Linear Equation Systems, Roman Domination in Complementary Prism Graphs, On Pathos Total Semitotal and Entire Total Block Graph of a Tree, Distance Two Labeling of Generalized Cacti, Degree Splitting Graph on Graceful, Felicitous and Elegant Labeling, and other topics. Contributors: Agboola A.A.A., Adeleke E.O. Akinleye S.A., B.Chaluvaraju, V.Chaitra, P.Selvaraju, P.Balaganesan, J.Renuka, V.Balaj, Suhua Ye, Yizhi Chen, Hui Luo, and others.