Author's response: co-trimoxazole treatment in idiopathic pulmonary fibrosis. Issue 9 (21st June 2013) - Shulgina, Ludmila; Cahn, Anthony P; Chilvers, Edwin R; Parfrey, Helen; Clark, Allan B; Wilson, Edward C F; Twentyman, Orion P; Davison, Anthony G; Curtin, John J; Crawford, Michael B; Wilson, Andrew M