Hughes RJ, Hopkins RJ, Hill S, Weatherall M, Van de Water N, Nowitz M, Milne D, Ayling J, Wilsher M, Beasley R. Frequency of venous thromboembolism in low to moderate risk long distance air travellers: the New Zealand Air Traveller's Thrombosis (NZATT) study. Lancet. 2003 Dec 20;362(9401):2039–44. doi: 10.1016/s0140-6736(03)15097-0. PMID: 14697802.