Leonard Wheeler

Effect of first-grade classroom environment on shy behavior, aggressive behavior, and concentration problems

S. Kellam, Sheppard Kellam, L. Werthamer-Larsson, 1991, American journal of community psychology.

The short-term impact of two classroom-based preventive interventions on aggressive and shy behaviors and poor achievement

George W. Rebok, Lawrence S. Mayer, Carla Ford, 1993 .