A year or so ago, I was looking into a problem that involved a lot of coins with different probabilities of flipping heads. The probability that $\displaystyle n$ heads would be flipped among all of the coins follows a Poisson distribution. I saved an article that I planned to look over more carefully that discussed using the mean probability of flipping heads along with the standard deviation among the coins to convert it to a system that seemed (to me) more similar to a Binomial distribution. I seem to recall that it involved a formula that used the cube of the standard deviation (maybe), but beyond that, I can't recall much about the article. I have no clue where I saved it. Does anyone know where I can find the article again? I apologize for my lack of information. I really have no clue what I did with it.