Coşkun, Turgay, et al. “Guanosine Triphosphate Cyclohydrolase I Deficiency: A Rare Cause of Hyperphenylalaninemia”. The Turkish Journal of Pediatrics, vol. 41, no. 2, Apr. 1999, pp. 231-7, https://doi.org/10.24953/turkjpediatr.1999.3225.