1. Bottos M, Dalla Barba B, Stefani D, et al. Locomotor strategies preceding independent walking: A prospective study of neurological and language development in 424 cases. Dev Med Child Neurol 1989;31:25–4.
2. Bulbena A, Duro JC, Porta M, et al. Clinical assessment of hypermobility of the joints: assembling criteria. J Rheumatol 1992;19:115–21.
3. Crombag H, Sleijpen F. Billenschuiven, kan of wil ik niet anders? Tijdschr NVFK 1999;26:8–11.
4. Empelen R van. Tonusonderzoek bij kinderen. Houten: Bohn Stafleu Van Loghum, 1996.
5. Eijsermans MJC. Motor performances after bottom–shuffling in early childhood. Physiotherapy 2000;86:81–4.