No free Hadeland catalogues on the net, Iím afraid. They are few and far between even in secondhand bookshops here in Norway, and only the art glass section of the catalogues list the various designers.
The rules for signed Willy Johansson is as follows: in the 1950s youíll find his pieces marked Hadeland WJ and the year (and sometimes the initials of the glassblower as well). His 1960s pieces are marked Hadeland, a model number in the 2000 range, plus WJ. In the 1970s and 80s they are only signed Hadeland WJ.
However, Willy Johansson designed probably close to 1500 models in his time at Hadeland - apart from the art glass he designed wine glasses, decanters, lamps etc. These were not signed, and nobody seems to have a complete grasp of his work. Even collectors struggle to identify unsigned pieces now and then.
Your best bet is to Google patiently, and post specific images or questions here on Glass Message Board.