The term 'sole source' refers to a situation in which a company or organization is the only provider of a particular product or service. In this context, the crossword solutions for the term 'sole source' are 'Dover' (5 letters) and 'ROE' (3 letters). Dover is a city in Delaware, USA, and ROE is a surname of English origin. Both words can be used to refer to a single source of something, such as a supplier or provider.