Feasibility and design of a trial regarding the optimal mode of delivery for preterm birth: the CASSAVA multiple methods study oleh Jane E Norman, Julia Lawton, Sarah J Stock, Dimitrios Siassakos, John Norrie, Nina Hallowell, Sushila Chowdhry, Ruth I Hart, David Odd, Jane Brewin, Lucy Culshaw, Caroline Lee-Davey, Hannah Tebbutt, Sonia Whyte