The Chaucer Review: An Indexed Bibliography (Vols. 1-30)

Robbins, Rossell Hope. "Geoffroi Chaucer, Poète Français, Father of English Poetry." 13 (1978): 93-115.
Chaucer's early work is lost, though scholars conjecture that because the courts of Chaucer's early life were French-speaking, his early poetry was French. French continued to be used as a court language until approximately 1417, though it continued to be the professed language of noble families for some time thereafter. Chaucer's wife also spoke French and probably Flemish. The Book of the Duchess was not written in French because a small audience for English poetry was growing at the aristocratic level. Also, Chaucer probably wrote the Book of the Duchess to read before the personal staff of the Duke of Lancaster, most of whom spoke English. Certainly, Chaucer's early works followed the French tradition in a manner similar to that of Michael de la Pole, Duke of Suffolk. Anonymous French poems, while not attributable to Chaucer, may be considered similar to courtly love lyrics Chaucer may have composed. Chaucer borrowed heavily from French works by Machaut and Froissart as well as the anonymous Songe Vert. Froissart and Machaut, not earlier French romances, were his models for the Book of the Duchess.