Yes, FMOLS (Fully Modified OLS) and DOLS (Dynamic OLS) can both be applied to the same dataset as complementary methods to check the robustness of long-run cointegration relationships. Although FMOLS is non-parametric and DOLS is parametric, both correct for endogeneity and serial correlation in different ways. Applying both helps verify the stability and reliability of the estimated coefficients. If results from both methods are consistent, it strengthens the confidence in the findings. This dual approach is common in empirical economics to ensure robustness, especially when dealing with small samples or uncertainty about model specification.