Found 1 pathways with zero (PubMed) references
http://classic.wikipathways.org/instance/WP381_rr117333 'Riboflavin, FMN, and FAD biosynthesis' in Saccharomyces cerevisiae has zero references;
More details at https://wikipathways.github.io/WikiPathwaysCurator/ReferencesTests/atLeastOneReference