This website offers phylogenetic information and also serves as a general reference guide to plant families. While the website focuses on angiosperms, there is some coverage of all land plants.

The International Plant Names Index (IPNI) is a database of the names and associated primary source citations of seed plants, ferns, and lycophytes.

Database of plant names. Records include images, botanical specimens information, and citations to the primary literature.

Database of herbaria collections. Entries include acronym, physical location, URL, contents (e.g., number and type of specimens), founding date, as well as names, contact information, and areas of expertise of associated staff.

Google Scholar enables you to search for literature, including peer-reviewed papers, theses, books, preprints, abstracts, and technical reports from all broad areas of research. However, it indexes these items automatically and you should take care to verify the scholarly nature of items you find. Additionally, sometimes the OU Article Linker does not work correctly from Google Scholar results; in those cases take the title, journal, or authors and search in a database from the Libraries website.

A list of databases available from FirstSearch on various subjects, including AnthropologyPlus, ArticleFirst, ClasePeriodica, Ebooks, ECO (Electronic Collections Online), ERIC, GEOBASE, GPO, History of Science, Technology and Medicine, Medline, OAIster, PapersFirst, Proceedings, World Almanac, WorldCat, and WorldCat Dissertations.