Cite the scanned version of the original dicionary like this:
Toller, T. Northcote, and Joseph Bosworth. "sæltna." An Anglo-Saxon Dictionary: Based on the Manuscript Collections of the Late Joseph Bosworth : Supplement. Oxford: Clarendon Press, 1921. 692.
(?)a bird's name :-- Saeltna, Wrt. Voc. ii. 119, 37 : seltra, i. 281, 8 : salthaga, 62, 36 gloss rubisca which is in the last case also glossed by rudduc the robin redbreast, v. rudduc.