Oxford Music Online
Contains Grove Music Online, the primary English-language reference source for music, and the New Grove Dictionary of Opera, both of which have articles on Wagner. Covers music of all styles, periods, and geographic regions. Note the extensive bibliographies in these articles.
Oxford Music Online Articles from The New Grove Dictionary of Opera
Oxford Bibliographies Online. Music. Highly recommended.
See especially the article on Richard Wagner. (If this direct link doesn't work, link to the whole work and then click on W in the blue alphabet buttons.)
This source is a guide to scholarly literature about music. It contains a growing number of articles on topics and individuals, with extremely useful bibliographies of recommended resources. Cross-searching with other modules of Oxford Bibliographies Online is possible in Advanced Search.
Richard Wagner: A Research and Information Guide. 2nd ed. By Michael Saffle. 2010. (print) Highly recommended.
MUSICMEDIA REFERENCE ML134 .W1 S24 2010
A very useful bibliography of Wagner research. This is kept in the reference section and does not check out.
Harvard Dictionary of Music, 4th ed. Don Michael Randel, ed. Cambridge, MA: Belknap Press of Harvard University Press, 2003
An authoritative source for definitions and concise articles on musical topics and terms. No articles on people.
Link directly to this book directly OR go to Credo Reference, use "Find a Book," limit your results to music books, and select only this title or all music titles.
Location of library's printed copy: MUSICMEDIA REFERENCE ML100 .H37 2003