Charles W. Eliot, the president of Harvard in 1869, initiated a system under which mos required courses were dropped in favor of elective courses.
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Population growth rates vary among regions and even among countries within the same region.
Biogas can be utilized for electricity production, cooking, space heating, water heating and process heating.
Around 150 B.C. the Greek astronomer Hipparchus developed a system to classify stars according to brightness.