1. Obstructive pulmonary disease: national clinical guideline on management of chronic obstructive pulmonary disease in adults in primary and secondary care;National Institute for Clinical Excellence;Thorax,2004
2. Chronic obstructive pulmonary disease in non-smokers;Salvi;Lancet,2009
3. Clearing the air: a national study of chronic obstructive pulmonary disease;Healthcare Commission,2006
4. Prevalence of COPD in Spain: impact of undiagnosed COPD on quality of life and daily life activities;Miravitlles;Thorax,2009
5. Chief Medical Officer. Annual Report of the Chief Medical Officer 2004 on the state of public health. Department of Health Publications; 2004.