Sumer is icumen in
London, British Library, MS Harley 978, f. 11v

Booklist

Bell, Nicolas, Music in Medieval Manuscripts (London: British Library, 2001)

Bukofzer, Manfred F., '"Sumer is icumen in": a revision', University of California Publications in Music 2 (1944), 79-114

Coates, Alan. English medieval books: the Reading Abbey collections from foundation to dispersal (Oxford: Clarendon, 1999)

Dobson, E. J., and F. Ll. Harrison, Medieval English Songs (London: Faber & Faber, 1979)
A critical edition of   the 33 ME lyrics which have survived with their music from before 1400, including texts, translations, and music.

Duffin, Ross W., 'The Sumer Canon: A New Revision', Speculum 63 (1988), 1-21

Handschin, Jacques, 'The Summer Canon and its Background', Musica Disciplina 3 (1949), 55-94; 5 (1951), 65-113

Fischer, A. '"Sumer is icumen in": the seasons of the year in Middle English and Early Modern English." Topics in English Linguistics 1994 (13), 79-96

Hohler, Christopher, 'Reflections on some MSS containing 13th-century Polyphony', Journal of the Plainsong and Medieval Music Society 1 (1978), 2-38

Lossef, Nicky, The Best Concords: Polyphonic Music in Thirteenth-Century Britain. New York: Garland, 1994

Masters, Bernadette A, 'Computer Editing of medieval Texts: A Caveat', Literary and Linguistic Computing 8 (1993), 131-41

Nares, R., and F. Douce, A Catalogue of the Harleian Manuscripts in the British Museum,   4 vols. (1808-12), vol. 1 (1808) pp. 488a--489b
In Latin. Includes a fairly full description of the contents of Harley 978.

Obst, W. '"Svmer is icumen in": A Contrafactum?' Music and Letters, 64 (1983), 151-61

Platzer, H. 'On the Disputed Reading of "Uerteth" in the "Cuckoo Song".' Neuphilologische Mitteilungen 96 (1995), 124-43

Roscow, G. H. 'What is "Sumer is icumen in"? Review of English Studies 50 (1999), 188-95

Schofield, B., 'The Provenance and Date of Sumer is icumen in', The Music Review (1948), 81-6

Silverstein, Theodore, ed. Medieval English Lyrics (London: Arnold, 1971)

Taylor, Andrew, Textual Situations: Three Medieval Manuscripts and their Readers (University of Pennsylvania Press, 2002)

Taylor, Andrew: for a bibliography of BL MS Harley 978, see  http://duke.usask.ca/~taylora/har978/biblio.htm.