Robert C. Tannehill, "The Magnificat as Poem." JBL 93 (1974): 263-75.
Tannehill examines the structure of the magnificat and concludes that the hymn holds together the small and the great--the birth of baby to an unimportant woman and the fulfillment of the divine promise to Israel through the reversal of societal values.
Weak on redemptive-historical connections with the Old Testament.