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Hegarty, Christopher J.; Chatre, Eric (December 2008). "Evolution of the Global Navigation satellite system (GNSS)". Proceedings of the IEEE. 96 (12): 1902–1917. doi:10.1109/JPROC.2008.2006090. S2CID838848.
Webber, M J (1980). "Literature for teaching quantitative geography: technique by, for, but not of geographers". Environment and Planning A. 12 (9): 1083–1090. Bibcode:1980EnPlA..12.1083W. doi:10.1068/a121083.
Walker, Robert Toovey (28 Apr 2021). "Geography, Von Thünen, and Tobler's first law: Tracing the evolution of a concept". Geographical Review. 112 (4): 591–607. doi:10.1080/00167428.2021.1906670. S2CID233620037.
Hegarty, Christopher J.; Chatre, Eric (December 2008). "Evolution of the Global Navigation satellite system (GNSS)". Proceedings of the IEEE. 96 (12): 1902–1917. doi:10.1109/JPROC.2008.2006090. S2CID838848.
Walker, Robert Toovey (28 Apr 2021). "Geography, Von Thünen, and Tobler's first law: Tracing the evolution of a concept". Geographical Review. 112 (4): 591–607. doi:10.1080/00167428.2021.1906670. S2CID233620037.