The standard work Collectible Stars by Stefan Wallrafen covers writing instruments only up to 1979 and therefore offers no complete data for the desired models of the 1980s; some devices are additionally missing there entirely. A suitable point of contact for historical catalogues and supplementary information is Stefan Wallrafen himself, who has(d) extensive material but has in recent years given up holdings. Even if some models were produced longer than stated, the production periods named in the book are reliable for most devices. Original dealer catalogues from the period 1980 to 1985 are the most reliable source for exact sales periods and prices.