Erika Schulz Wendy Cohen Anja Lowit Lisa Crampin Retrospective longitudinal analysis of phonetic and phonological cleft palate speech characteristics. 2015 ICPhS https://www.internationalphoneticassociation.org/icphs-proceedings/ICPhS2015/Papers/ICPHS0200.pdf conf/icphs/2015 db/conf/icphs/icphs2015.html#SchulzCLC15