BibTex format
@article{ASHBY:1993:10.1038/bjc.1993.481,
author = {ASHBY, D and MACHIN, D},
doi = {10.1038/bjc.1993.481},
journal = {BRITISH JOURNAL OF CANCER},
pages = {1047--1050},
title = {STOPPING RULES, INTERIM ANALYSES AND DATA MONITORING COMMITTEES},
url = {http://dx.doi.org/10.1038/bjc.1993.481},
volume = {68},
year = {1993}
}