Sampling and ethical issues in a multicenter study on health of people with intellectual disabilities

Marja Y. Veenstra, Patricia N. Walsh, Henny M.J. Van Schrojenstein Lantman-De Valk, Meindert J. Haveman, Christine Linehan, Mike P. Kerr, Germain Weber, Luis Salvador-Carulla, Alexandra Carmen-Cara, Bernard Azema, Serafino Buono, Arunas Germanavicius, Jan Tossebro, Tuomo Maatta, Geert Van Hove, Dasa Moravec