It is typical in this kind of inexact advertising to mention 10 years of long-term testing but not to substantiate the claims. The research mentioned does not stem from Lozanov. Even if it were documented, one could not scientifically ascertain for a large number of subjects that the material learned and stored 10 years ago had not been reviewed in the meantime, even though that might have been unintentional. While Lozanov (1978, p. 215) does indeed speak of exceptionally high memory retention (96-100%) for "many" groups after 2 years, only 1 table of data for 10 subjects is presented. Thus, the validity of his claims must also be questioned.