Drupal-Bibcite0<style face="normal" font="default" size="100%">Effect on health-related quality of life of ongoing feedback during a 12-month maintenance walking programme in patients with COPD: a randomized controlled trial</style><style face="normal" font="default" size="100%">Effect on health-related quality of life of ongoing feedback during a 12-month maintenance walking programme in patients with COPD: a randomized controlled trial</style>