deletions | additions       diff --git a/introduction.tex b/introduction.tex  index efaa07b..4b8de6f 100644  --- a/introduction.tex  +++ b/introduction.tex 
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\begin{equation}  h(x,y,z) =   \sum^{\infty}_{n=0} \sum^{\infty}_{m=0} exp \{ -2 \pi (k_x^2 +k_y^2)^{1/2} z \}   (A_{m} cos { }  2 \pi k_x x + B_{m} sin 2 \pi k_x x ) (C_{n} cos 2 \pi k_y y + D_{n} sin 2 \pi k_y y )  \end{equation}  em que $A_{n}, B_{n}$, $P_{m}, Q_{m}$ e $C$ s\ao constantes e $\lambda$ \'e um n\'umero positivo.