in the period from 1935 to 1938 milanković calculated that ice cover depended on changes in insolation. he succeeded in defining the mathematical relationship between summer insolation and the altitude of the snow line. in this way he defined the increase of snow which would occur as a consequence of any given change in summer insolation. he published his results in the study ""new results of the astronomic theory of climate changes"" in 1938. geologists received a graph for presenting bordering altitudes of ice covers any period of time during the last 600,000 years. andré berger and jacques laskar later developed this theory further.