Hi Jim,
I looked this up on SMIC for you (
www.mic.se). It was published by a group called NMS, now apparently held by Gehrmans. Here are the publisher details they give for Olson's Requiem in G minor Op.13:
Gehrmans Musikförlag
Address: Box 42026
Telephone: vxl 08-610 06 00 återförsäljare 08-610 06 01
Fax: 08-610 06 27
E-mail: info@gehrmans.se
Web:
www.gehrmans.se Publisher code: Abr Lundquist, Abr.L, NMS, WHS, Gehrman, SK-Gehrman, SSKB, CG, SK-CG, SKG, SK, Hirsch, SSF, Choragus, KMH-förlaget, Pygmé, Körling, Carl Johnn's, WarnerChappell
Rec code: Gehrman, Sveriges körförb
I hope that helps.