@jepcastel

Those confounded vitamins: what can we learn from the differences between observational versus randomised trial evidence?

, , , , and . Lancet, 363 (9422): 1724-7 (May 2004)3635<m:linebreak></m:linebreak>Tipus d&#039;estudis.
DOI: 10.1016/S0140-6736(04)16260-0