Complete the following sentence: Riffenburgh earned his doctorate degree at the Scott Polar Research Institute at the University of Cambridge. ️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️
Nimrod Expedition, which almost reached both the South Pole and the South Magnetic Pole; and "Racing with Death", the story of Douglas Mawson's Antarctic expeditions. He was the editor of the "Encyclopedia of the Antarctic", a two-volume work that is the most comprehensive reference work ever produced about the Antarctic.