The FOMC minutes for the March 17-18, 2015 meeting.
This is the key passage:
"Several participants judged that the economic data and outlook were likely to warrant beginning normalization at the June meeting. However, others anticipated that the effects of energy price declines and the dollar's appreciation would continue to weigh on inflation in the near term, suggesting that conditions likely would not be appropriate to begin raising rates until later in the year, and a couple of participants suggested that the economic outlook likely would not call for liftoff until 2016."
