Hetu , J.-F. ., A. . Fortin, and D. H. . Pelletier. “An a Posteriori Error Estimator for the Navier-Stokes Equations”. European Journal of Computational Mechanics, vol. 3, no. 3, Mar. 1994, pp. 363-77, https://journals.riverpublishers.com/index.php/EJCM/article/view/3613.