Fòram na Gàidhlig

Hello everyone, long time no see. I am going through some bibliographical notes and keep coming across the abbreviation 'deas.' like in the below example:

See ‘Dòmhnall Ruadh Chorùna’ (deas. le Fred MacAmhlaidh, 1995) p. 58.

I know that 'le' shows authorship (like 'by') but what does 'deas.' mean in this context? It keeps cropping up.

Móran taing!

deasachadh - edition

Ahhh excellent, móran taing.

deasaichte le X - edited by X

Cha robh mi cinnteach ciamar a bhios seo sa Bheurla
Tapadh leat, a Neill!

'S e do bheatha, a Mhared!

Obh! Tapadh leat, a Neill!