Quiring, S. M; Papakryiakou, T. N. (2003). "An evaluation of agricultural drought indices for the Canadian prairies". Agricultural and Forest Meteorology. 118 (1–2): 49–62. Bibcode:2003AgFM..118...49Q. doi:10.1016/S0168-1923(03)00072-8.
Quiring, S. M; Papakryiakou, T. N. (2003). "An evaluation of agricultural drought indices for the Canadian prairies". Agricultural and Forest Meteorology. 118 (1–2): 49–62. Bibcode:2003AgFM..118...49Q. doi:10.1016/S0168-1923(03)00072-8.
Quiring, S. M; Papakryiakou, T. N. (2003). "An evaluation of agricultural drought indices for the Canadian prairies". Agricultural and Forest Meteorology. 118 (1–2): 49–62. Bibcode:2003AgFM..118...49Q. doi:10.1016/S0168-1923(03)00072-8.
Quiring, S. M; Papakryiakou, T. N. (2003). "An evaluation of agricultural drought indices for the Canadian prairies". Agricultural and Forest Meteorology. 118 (1–2): 49–62. Bibcode:2003AgFM..118...49Q. doi:10.1016/S0168-1923(03)00072-8.
internationalboundarycommission.org
"The Boundary". International Boundary Commission. 1985. Archived from the original on 1 August 2008. Retrieved 17 May 2012.