Biodiversity Heritage Library
The Biodiversity Heritage Library (BHL) is an online library providing free and open access to the legacy literature of taxonomy and biodiversity. Materials in BHL are provided by a consortium of natural history and botanical libraries who have come together to digitize the literature of biodiversity held in their collections and to make it available as part of a global 'biodiversity commons.' The bulk of material in the BHL is in the public domain in the United States, meaning that the publication date is prior to 1923. Many of the collections contain rare published literature previously available only to those who could visit the institutions.