Addressing the tensions and complexities involved in commissioning and undertaking implementation research in low- and middle-income countries. Issue 4 (12th July 2018) - Doherty, Tanya; Lewin, Simon; Kinney, Mary; Sanders, David; Mathews, Cathy; Daviaud, Emmanuelle; Goga, Ameena; Bhana, Arvin; Besada, Donela; Vanleeuw, Lieve; Loveday, Marian; Odendaal, Willem; et al.