Cite the scanned version of the original dicionary like this:
Toller, T. Northcote, and Joseph Bosworth. "æcer." An Anglo-Saxon Dictionary: Based on the Manuscript Collections of the Late Joseph Bosworth : Supplement. Oxford: Clarendon Press, 1921. 755.
, æcyr, es; m.I.a field, land, what is sown, sown land; ager, seges :-- For ðam is se æcer geháten Acheldemah propter hoc vocatus est ager ille Haceldama, Mt. Bos. 27, 8. Hér ys seó bót, hú ðú meaht ðíne æceras betan here is the remedy, how thou mayest improve thy fields, Lchdm. i. 398, 1. Of ðæm æcere from the field, Bt. Met. Fox 12, 3; Met. 12, 2. Æcera þúsend a thousand fields, 14, 10; Met. 14, 5. II. a definite quantity of land which, in A.