title: On the etiology of recurring oral ulcers.
mesh_terms: D006560:Herpes Labialis / Q000209:etiology*; D006801:Humans; D018139:Simplexvirus / Q000276:immunology* / Q000472:pathogenicity*; D013281:Stomatitis, Aphthous / Q000209:etiology*; D014776:Virus Cultivation