«Section 1.1». A: Official Volleyball Rules 2011-2012 (PDF). FIVB, 2010 [Consulta: 27 octubre 2011]. «The playing court is [...] surrounded by a free zone which is a minimum of 3 m wide on all sides.»
«Section 3.1». A: Official Volleyball Rules 2011-2012 (PDF). FIVB, 2010 [Consulta: 27 octubre 2011]. «STANDARDS The ball shall be spherical(...)»