See, e.g., Bullitt (2005), entry for "viriya," which defines this term as: "Persistence; energy. One of the ten perfections (paramis), the five faculties (bala; see bodhi-pakkhiya-dhamma), and the five strengths/dominant factors (indriya; see bodhi-pakkhiya-dhamma)." Retrieved 3 Feb. 2011 from "ATI" at http://www.accesstoinsight.org/glossary.html#viriya .