1. Fletcher and Oldham (1949) Blair et al. (1966) Ashford et al. (1965)
2. including trial A, this paper) Cochrane,1962
3. Liddell and May (1966); Jacobsen;Liddell (1963), Liddell; Lindars,1969
4. Eyssen and Liddell (in preparation);UICC Committee,1970
5. The pneumoconioses: methods of measuring progression;Amandus, H.E.; Reger, R.B.; Pendergrass, E.P.; Dennis, J.M.; Morgan, W.K.C.;Chest,1973