Kahraman, Ayca Burcu, et al. “Impact of the COVID-19 Era on Phenylalanine Levels and Classical Phenylketonuria Patients Follow-Up: A Retrospective Analysis”. Turkish Journal of Pediatric Disease, vol. 19, no. 2, Mar. 2025, pp. 59-63, https://doi.org/10.12956/tchd.1537456.