On Grothendieck--Serre conjecture in mixed characteristic for SL_1(D)

Let R be an unramified regular local ring of mixed characteristic, D an Azumaya R-algebra, K the fraction field of R, Nrd the reduced norm homomorphism for the Azumaya R-algebra D. Let a be a unit in R. It is proved the following: suppose the equation Nrd=a has a solution over K, then it has a solution over R. Similar results are proved for regular local rings, which are geometrically regular over a discrete valuation ring of mixed characteristic. These results extend result proven by A.Sulin and the author in the middle of 90’s.