1. Cho, I.: Graph Groupoids and Partial Isometries, ISBN:978-3-8383-1397-9. LAP Publisher, Saarbrücken (2009)
2. Cho, I.: K-Theory on Groupoid Algebras Induced by Graphs (2011, Submitted to ACTA Appl. Math.)
3. Cho, I.: Operations on Graphs, Groupoids, and Operator Algebras, ISBN:978-8383-5271-8. LAP Publisher, Saarbrücken (2010)
4. Cho, I.:Operator algebraic quotient structures induced by directed graphs. Comput. Anal. Oper. Theory. doi: 10.1063/1.3056588 (2010)
5. Cho, I.: Index on von Neumann algebras induced by graphs. Appl. Math. Sci. (2011, in press)