The importance and need for unique, persistent identifiers for reliable access to published literature has become widely accepted, and the literature for the biodiversity informatics community is no exception. For published works, these generally take the form of Digital Object Identifiers (DOIs). BHL has been consistently assigning CrossRef DOIs to monographic publications for three years. However, the number of items in BHL with DOIs remains relatively small with just over 68,000 assigned to date. In addition to the remaining monographs, BHL now also has over 140,000 articles identified, primarily via BioStor.