A Weak Opening System by Lukasz Slawinski (and Stanislaw Ruminski) 1970, published in english as booklet in 1974. Regres is an improvement of the ANTIDELTA system (1969). Hands with a HCP of 8-12 are the most common. The idea is that it will be better to open these hands instead of passing first and , if possible and not too risky, to overcall afterwards, because the opponent exchanged information already. Nice condition but plasticised cover and a few rubber stamp marks inside covered up.