Level 9

Adventureland: Level 9 Computing - http://www.if-legends.org/~adventure/Level_9_Computing.html
Short company information and a detailed list of the adventures they published.

Level 9: Past Masters of the Adventure Game - http://www.waddington.fslife.co.uk/level9.htm
Article by Richard Hewison from Classix Fanzine.

Sinclair User: On the level - http://www.sincuser.f9.co.uk/038/htsquad.htm
"Another time, another space. Chris Bourne reaches Level 9" Interview with Nick and Pete Austin of Level 9.

The Dungeon Masters - http://www.nvg.ntnu.no/sinclair/industry/publishers/level9_su0585.htm
Interview with Pete Austin of Level 9.

The Level 9 Fact List - ftp://ftp.gmd.de/if-archive/level9/info/Level9_Facts.txt
Comprehensive source of information on Level 9 games and packaging.