Cite the scanned version of the original dicionary like this:
Bosworth, Joseph. "feald." An Anglo-Saxon Dictionary: Based on the Manuscript Collections of the Late Joseph Bosworth. Ed. Thomas Northcote Toller. Oxford: Clarendon Press, 1898. 271.
fold (as a multiplicative) :-- Þæt man ǽlcne ceáp mihte be twám fealdum (be twiefealdan, S. 248, 2) bet geceápian þonne man ǽr mihte ut duplicia quam usque ad id fuerant rerum venalium pretia statuerentur, Ors. 5, 13; Bos. 113, 37. [O. H. Ger. falt plica: Icel. faldr.] v. fela-, þic-feald ; fild.