Grant, Aileen, Dean, Sarah, Hay-Smith, Jean, Hagen, Suzanne, McClurg, Doreen, Taylor, Anne, Kovandzic, Marija, Bugge, Carol, "Effectiveness and cost-effectiveness randomised controlled trial of basic versus biofeedback-mediated intensive pelvic floor muscle training for female stress or mixed urinary incontinence: protocol for the OPAL (optimising pelvic floor exercises to achieve long-term benefits) trial mixed methods longitudinal qualitative case study and process evaluation.", BMJ open, 2019