Cite the scanned version of the original dicionary like this:
Toller, T. Northcote, and Joseph Bosworth. "ofer-swíþe." An Anglo-Saxon Dictionary: Based on the Manuscript Collections of the Late Joseph Bosworth : Supplement. Oxford: Clarendon Press, 1921. 661.
;adv. Over-much, loo much :-- Sý hé snotor and ná oferswíðe ne þreáge, R. Ben. 121, 3. Ða heáfodmen lufedon swíðe and oferswíðe gítsunge on golde and on seolfre. Chr. 1086; Erl. 220, 5. [Ouermuchel and ouerswuðe ivonded, A. R. 178, 9.]