Clinical trials in cancer screening, prevention and early diagnosis (SPED): a systematic mapping review oleh Emma L. O’Dowd, Samuel W. D. Merriel, Vinton W. T. Cheng, Sam Khan, Lynne M. Howells, Dipesh P. Gopal, Elizabeth A. Roundhill, Paul M. Brennan, Philip A. J. Crosbie, Richard D. Neal, Karen Brown, Emma J. Crosbie, David R. Baldwin