On the unbounded of a class of Fourier integral operator on $L^2(R^n)$

In this paper, we give an example of Fourier integral operator with a symbol belongs to $\bigcap _{0<\rho <1}{S}_{\rho ,1}^0$ that cannot be extended as a bounded operator on $L^2({\mathbb{R}}^n)\mathrm{.}$