Determining energy spectra for separate mass groups from EAS: the quest is still on

Among the most suitable extensive air showers observables to determine mass and energy of primary cosmic ray particles are electron and muon sizes recorded on observation level. Some methodical aspects of such procedures are investigated. It is shown that it is necessary to make full use of the correlations between these two observables in order to obtain unambiguous results. This is in contradiction to recent claims in literature.