In 1965 , John Hajnal discovered it divides Europe into two areas characterized by different levels of nuptiality .
The Hajnal line is a border that links Saint Petersburg , Russia and Trieste , Italy .
In 1965 , Hajnal   discovered it divides Europe into two areas characterized by different levels of nuptiality .
The Hajnal line is a border that links Saint Petersburg , Russia and Trieste , Italy .