Three minor clarifications... first, our article on radioactivity is a redirect to "Radioactive decay,"
http://en.wikipedia.org/wiki/Radioactive_decay
and that's the article to which my comments apply.
Second, the Encyclopaedia Britannica Eleventh Edition's article on "Radioactivity" is considerably _longer_ than ours, so an equivalent citation density in ours would be less than fifty-four inline citations... I haven't got time to do the math right now but since our article has zero citations the ratio is still the same.
Third, no, just for the record, I don't think E. Ru.'s 1911 article would be the best article to rely on, as of 2006, as one's sole source of information on radioactivity, a few things having been learned in the last century....