(Minneapolis, MN) -- Nurses from Saint Luke's Hospital and Saint Mary's Duluth Clinic did another round of informational picketing yesterday. Union leaders indicated contract negotiations are centered around staffing levels. Nancy Carlson, an RN at Saint Luke's, says they want to make sure there are enough nurses for the patients. Hospital officials say their nurses have the right to do an informational picket and they respect their rights. Carlson says unless a contract agreement is reached, the Duluth nurses are set to vote August 18th whether to go out on a one-day strike.