Tác giả: William A. (Michigan State University) Donohue

Even in the flattest landscape there are passes where the road first climbs to a peak and then descends into a new valley. Most of these passes are simply topography with little or no difference in c …

Even in the flattest landscape there are passes where the road first climbs to a peak and then descends into a new valley. Most of these passes are simply topography with little or no difference in c …