Oregon's senators on Tuesday asked Douglas County and the Cow Creek Band of the Umpqua Tribe of Indians to work together to resolve the "impasse" over the tribal land transfer issue.Sens. Gordon Smith and Ron Wyden signed a joint letter sent to the Douglas County Board of Commissioners asking the county and the tribe to "find a constructive and mutually beneficial resolution of the current impasse." An identical letter was sent to Sue Shaffer, the tribal chairwoman.Douglas County Commissioner Dan Van Slyke said he was encouraged by the entry of the senators and their desire to have the situation worked …