Journal of Geometry and Physics
Journal of Geometry and Physics > 2011 > 61 > 4 > 815-828
Journal of Geometry and Physics > 2011 > 61 > 5 > 890-898
Journal of Geometry and Physics > 2011 > 61 > 4 > 815-828
Journal of Geometry and Physics > 2011 > 61 > 5 > 890-898