Macdonald A, Davies P, Daly A, Hopkins V, Hall SK, Asplin D, Hendriksz C, Chakrapani A. Does maternal knowledge and parent education affect blood phenylalanine control in phenylketonuria? J Hum Nutr Diet. 2008 Aug;21(4):351–8. doi: 10.1111/j.1365-277x.2008.00891.x. PMID: 18721402.