Cite the scanned version of the original dicionary like this:
Toller, T. Northcote, and Joseph Bosworth. "á-breátan." An Anglo-Saxon Dictionary: Based on the Manuscript Collections of the Late Joseph Bosworth : Supplement. Oxford: Clarendon Press, 1921. 4.
;p. -breót, pl. -breóton To break, kill; frangere, concidere, necare :-- Abreót brim-wísan, brýd aheorde slew the sea-leader, set free his bride, Beo. Th. 5852; B. 2930. v. a-breótan.