1. In the 1980 ILO classification of radiographs it is specified that the overall profusion of small opacities should be recorded; with the previous version of the classification the profusions of rounded and irregular opacities were recorded separately. The reasons for the Butterworths,1982
2. Pulmonary ventilatory function in coalminers in various areas in relation tox-ray category of pneumoconiosis;Cochrane, A.L.; Higgins, I.T.T.;BrJ Prevent Soc Med,1961
3. Role ofdust in the workingenvironment inthe development ofchronic bronchitis in British coal mines;Rogan, J.M.; Attfield, M.D.; Jacobsen, M.; Rae, S.; Walker, D.D.; Walton, W.I.H.;Br J Indust Med,1973
4. Lung mechanics and frechange were specified'9 but a consequence in our study quency dependence of compliance in coal miners;Seaton, A.; Lapp, N.L.; Morgan, W.K.C.,1972
5. the profusions of the two types ofopacity