What are the rules for the earliest one can take distributions from an IRA? Cites?

According to IRS Publication 590, there are no minimum age restrictions for taking distributions from an IRA. However, if they are taken prior to age 59-1/2, they are subject to a 10% premature distribution penalty unless one of the exceptions is met.

One of these exceptions is a series of substantially equal periodic payments over the life expectancy of the taxpayer (or joint expectancies of the taxpayer and beneficiary). Thus, if a "life income" is taken, there is no minimum age at which it can begin, and it is not subject to the penalty.

Hope this helps.