Asymptotic Distributions of Seasonal Unit Root Tests: A Unifying Approach
Denise Osborne, Paulo M. M. Rodrigues
Econometric Reviews, vol. 21, 2002, p. 221-241.

Performance of Seasonal Unit Root Tests for Monthly Data
Paulo M. M. Rodrigues, Denise Osborne
Journal Of Applied Statistics, vol. 26, 1999, p. 985-1004.