1. Sur une inégalité;Opial;Ann. Polon. Math.,1960
2. Opial type inequalities involving fractional derivatives of functions;Anastassiou;Nonlinear Studies,1999
3. The Riemann-Liouville integral;Canavati;Nieuw Archief Voor Wiskunde,1987
4. Opial Inequalities with Applications in Differential and Difference Equations;Agarwal,1995
5. General fractional Opial type inequalities;Anastassiou;Acta Applicandae Mathematicae,1998