Cite the scanned version of the original dicionary like this:
Toller, T. Northcote, and Joseph Bosworth. "sand-geweorp." An Anglo-Saxon Dictionary: Based on the Manuscript Collections of the Late Joseph Bosworth : Supplement. Oxford: Clarendon Press, 1921. 694.
, es; n. A sand-bank, quicksand :-- Sandgewurp syrtis, Wrt. Voc. i. 63, 72. On sandgeweorp in sirtim, ii. 45, 66. [Cf. O. H. Ger. sant-wurfi syrtis.] v. next word and sand-hrycg.