1993 | World Health et al

2011 | Katherine Rogers et al

2009 | Shirley Bach et al

2015 | Maharashtra University et al

2002 | Kaplan

2009 | Anthony R. Kovner PhD Ann S. McAlearne et al

2008 | James M Ritter, Lionel D Lewis, Timothy GK Mant et al

2012 | Essentially Holistic

2006 | Jim Swan

2013 | OpenStax College