1. Die angeborenen fisteln der unterlippe and ihre Entstehung;Stieda;Arch Klin Chir,1906
2. Congenital fistulas of the lower lip. Report of a case;Phillips;J Oral Surg,1968
3. Midline sinuses of the upper lip. Case report;Grenman;Scand J Plast Reconstr Surg,1985
4. Pits of the lip commissures in Caucasoid males;Baker;Oral Surg Oral Med Oral Pathol,1966
5. The syndrome of pits of the lower lip and cleft lip and or palate. Genetic considerations;Cervenka;Am J Hum Genet,1967