Development and validation of ester impregnated pH strips for locating nasogastric feeding tubes in the stomach—a multicentre prospective diagnostic performance study oleh Melody Ni, Mina E. Adam, Fatima Akbar, Jeremy R. Huddy, Simone Borsci, Peter Buckle, Francesca Rubulotta, Reuben Carr, Ian Fotheringham, Claire Wilson, Matthew Tsang, Susan Harding, Nichola White, George B. Hanna