More Groups
Fewer Groups
More People
Fewer People
Wessler, J. D.; Steingart, R. M.; Schwartz, G. K.; Harvey, B. G.; Schaffer, W. Chest (2010)
Feinstein, M. B.; Ostroff, J. S.; Park, B. J.; Coups, E. J.; Steingart, R. M.; Burkhalter, J. Chest (2007)