Original:  however, since that time, a number of different  definitions have emerged , with some contradicting others .Vijayaraghavan, L., Krishnamoorthy, E. S., Brown, R. G., & Trimble, M. R. (2002).
Revised:  however, since that time, a number of different definitions have emerged .Vijayaraghavan, L., Krishnamoorthy, E. S., Brown, R. G., & Trimble, M. R. (2002).
Edit intent: clarity