I want to used the funtion ur.ers (DF-GLS unit root test) from the urca packet, but there is not a test which give me the optimal lags in the posibilities of the packet. I am interested in know if there is a program to calculed this optimal lag, or if someone know which one is the maximal criterium used in the maximization of the function using to obtain this unit root criterium. Thank you very much for your help in advance, -- -- Karla Hernández Department für Agrarökonomie und Rurale Entwicklung Universität Göttingen Platz der Göttinger Sieben 5 37073 Göttingen Tel.: 0551/39-4828 [[alternative HTML version deleted]]