Scanian raises are part of a very aggressive 4 card major system first popularized in Sweden and published by Mats Wilander. In general, an opening bid of 1M shows EITHER 4+ long with 11-13 balanced or 5+ long with 14+. (The opening bid of 1nt shows 14-16 flat and tends to deny a 5 card major.) In response, a single raise shows a bad hand (generally 4-8 HCPS, 3-4 card support, and 8-9 losers) while a double raise shows a distributionally sound single raise (generally 5-8 HCPs, 4+ support, and either a side singleton or two side doubletons). A double raise of 1S might be made with Kxxx; xx; KJxxx; xx. A response of 2nt shows a limit raise or better, and many artificial sequences follow.
I'd suggest you contact the Bridge World to see if the book _Scanian Raises_ is still available. I think it costs something like 9 bucks.