The S.A.S. DC-10's did indeed operate on behalf of Scanair (DK flight numbers, callsign "Viking") summer 1978 and summer 1979. 6 flights in'78, only 3 in '79 as I recall. Not on Sundays, though, Tuesdays mostly. See my post 664
http://www.pprune.org/8944482-post664.html
Best photo I have, unfortunately:-
LN-RKA LTN 25/7/78