Cite the scanned version of the original dicionary like this:
Bosworth, Joseph. "ofen-raca." An Anglo-Saxon Dictionary: Based on the Manuscript Collections of the Late Joseph Bosworth. Ed. Thomas Northcote Toller. Oxford: Clarendon Press, 1898. 729.
.Add:-racu, e ; f. For 'an instrument for clearing out an oven or furnace' substitute: 'A fork for stirring the fire in a furnace for cooking,' [Cf. rotabulum furca vel illud lignum cum quo ignis movetur in fornace causa coquendi, Migne] :-- Man sceal habban . . . ofnrace, Angl. ix. 265, 3.