Encyclopædia Britannica, Inc. is a Scottish-founded American company known for publishing the Encyclopædia Britannica, the world's oldest continuously published encyclopaedia, as well as extensive digital efforts—including text and audiovisual—that are aimed at educational tools for primary and secondary schools, and for everyday learners accessing information through online search.

Grolier was one of the largest American publishers of general encyclopedias, including The Book of Knowledge (1910), The New Book of Knowledge (1966), The New Book of Popular Science (1972), Encyclopedia Americana (1945), Academic American Encyclopedia (1980), and numerous incarnations of a CD-ROM encyclopedia (1986–2003).

Guinness World Records, known from its inception in 1955 until 2000 as The Guinness Book of Records and in previous United States editions as The Guinness Book of World Records, is a reference book published annually, listing world records both of human achievements and the extremes of the natural world. The brainchild of Sir Hugh Beaver, the book was co-founded by twin brothers Norris and Ross McWhirter in Fleet Street, London, in August 1954.

Langenscheidt is a privately held German publishing company that specializes in language reference works. In addition to publishing monolingual dictionaries, Langenscheidt also publishes bilingual dictionaries and travel phrase-books.

Martindale-Hubbell is an information services company to the legal profession that was founded in 1868. The company publishes the Martindale-Hubbell Law Directory, which provides background information on lawyers and law firms in the United States and other countries. It also published the Martindale Hubbell Law Digest, a summary of laws around the world. Martindale-Hubbell is owned by consumer website company Internet Brands.

Merriam-Webster, Inc., is an American company that publishes reference books and is especially known for its dictionaries.

Oxford University Press (OUP) is the university press of University of Oxford. It is the largest university press in the world, and the second oldest after Cambridge University Press. It is a department of the University of Oxford and is governed by a group of 15 academics appointed by the vice-chancellor known as the delegates of the press. They are headed by the secretary to the delegates, who serves as OUP's chief executive and as its major representative on other university bodies. Oxford University Press has had a similar governance structure since the 17th century. The Press is located on Walton Street, Oxford, opposite Somerville College, in the inner suburb of Jericho.

Routledge is a British multinational publisher. It was founded in 1836 by George Routledge, and specialises in providing academic books, journals and online resources in the fields of humanities, behavioural science, education, law, and social science. The company publishes approximately 1,800 journals and 5,000 new books each year and their backlist encompasses over 70,000 titles. Routledge is claimed to be the largest global academic publisher within humanities and social sciences.