Neville, Jonathan J;    den Uijl, Iris;    Irvine, Willemijn;    Eaton, Simon;    Gottrand, Frederic;    Hall, Nigel J;      (2025)    Development of a core outcome set for paediatric achalasia: a joint ERNICA, ESPGHAN and EUPSA study protocol.                   BMJ Paediatrics Open , 9  (1)    , Article e003130.  10.1136/bmjpo-2024-003130 <https://doi.org/10.1136/bmjpo-2024-003130>.       Green open access