This paper gives the existence of a duck solution in a slow-fast system in R2+2 using two ways. One is an indirect way and the other is a direct way. In the indirect way, the original system is once reduced to the slow-fast system in R2+1. In the direct one, it has a 4-dimensional duck solution when having an efficient local model. This is already published in [1,2]. Some sufficient conditions are given to get such a good model.
 S. A. Campbell and M. Waite, “Multistability in Coupled Fitzhugh-Nagumo Oscillators,” Nonlinear Analysis, Vol. 47, No. 2, 2000, pp. 1093-1104. http://dx.doi.org/10.1016/S0362-546X(01)00249-8
 A. K. Zvonkin and M. A. Shubin, “Non-Standard Analysis and Singular Perturbations of Ordinary Differential Equations,” Russian Mathematical Surveys, Vol. 39, No. 2, 1984, pp. 69-131.
 E. Nelson, “Internal Set Theory,” Bulletin of the American Mathematical Society, Vol. 83, No. 6, 1977, pp. 1165-1198.
 E. Benoit, “Canards et Enlacements,” Publications Mathématiques de l’IHéS, Vol. 72, No. 1, 1990, pp. 63-91.