Potential role of proprietary patent medicine vendors in primary eye and ear care: A mixed methods study in northern Nigeria - Joseph Okeibunor; Andrew Smith; Emma Jolley; Elizabeth Elhassan; Oluwatosin Adekeye; Lawal Hasfat Kontagora; Sunday Isiyaku; William Adamani; Caleb Mpyet; Hannah Faal; Elena Schmidt; Clare E. Gilbert (PLoS ONE, 2025)