Lashley, Morgan J. J. O.; Nauwelaerts, Sandra; Vernooij, J. C. M.; Back, W.; Clayton, Hilary M. (2014-12-01). "Comparison of the head and neck position of elite dressage horses during top-level competitions in 1992 versus 2008". The Veterinary Journal. 202 (3): 462–465. doi:10.1016/j.tvjl.2014.08.028. ISSN1090-0233. PMID25296851.
Lashley, Morgan J. J. O.; Nauwelaerts, Sandra; Vernooij, J. C. M.; Back, W.; Clayton, Hilary M. (2014-12-01). "Comparison of the head and neck position of elite dressage horses during top-level competitions in 1992 versus 2008". The Veterinary Journal. 202 (3): 462–465. doi:10.1016/j.tvjl.2014.08.028. ISSN1090-0233. PMID25296851.
Lashley, Morgan J. J. O.; Nauwelaerts, Sandra; Vernooij, J. C. M.; Back, W.; Clayton, Hilary M. (2014-12-01). "Comparison of the head and neck position of elite dressage horses during top-level competitions in 1992 versus 2008". The Veterinary Journal. 202 (3): 462–465. doi:10.1016/j.tvjl.2014.08.028. ISSN1090-0233. PMID25296851.