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

Owen, Charles A., Jr. "Pre-1450 Manuscripts of the Canterbury Tales: Relationships and Significance (Part II)." 23 (1988): 95-116.
No evidence suggests that any of the d manuscripts are the product of a group of scribes in a shop. The b manuscript group seems to have been produced after 1450. Three methods of manuscript production can be discerned after careful study. First, exemplars were gathered for specific occasions, resulting in manuscripts like Hengwrt, Harley 7334, Cambridge Dd, Ellesmere, and Cambridge Gg. Second, copies were made of pre-existing manuscripts. Third, a manuscript might be the product of amassing "exemplars made for a previous manuscript" (114).

Tschann, Judith. "The Layout of Sir Thopas in the Ellesmere, Hengwrt, Cambridge Dd.4.24, and Cambridge Gg.4.27 Manuscripts." 20 (1985): 1-13.
The presentation of the Tale of Sir Thopas in the Ellesmere, Hengwrt, and Cambridge manuscripts gives readers different ways of reading it, and suggests the ability of the scribes who presented the poem to read and understand the story they were copying as if it were a piece of architecture.