Caudwell Xtreme Everest: A prospective study of the effects of environmental hypoxia on cognitive functioning by Griva, K, Stygall, J, Wilson, M, Martin, D, Levett, D, Mitchell, K, Mythen, M, Montgomery, H, Grocott, M, Aref-Adib, G, Edsell, M, Plant, T, Imray, C, Cooke, D, Harrington, J, Khosravi, M, Newman, S, Basnyat, B, Caudwell Xtreme Everest Research Group