Coules Ε.Φ. and Tzetzis Γ. 2005. Systematic Observation of the Lesson of Physical Education with the Use Of OSCD-PE. Inquiries in Physical Education and Sport. 3, 3 (Dec. 2005), 204–211. DOI:https://doi.org/10.26253/heal.uth.ojs.ispe.2005.1091.