It is published in the June 1961 issue of Chess Life ( Elo 1978 : 197 ) .
1961 -- Elo develops his system and it is used by the USCF ( Harkness 1967 : 184 ) .
system is published in the June 1961 issue of Chess Life ( Elo 1978 : 197 ) .
1961 -- Elo develops his system and it is used by the USCF ( Harkness 1967 : 184 ) .