deletions | additions       diff --git a/introduction.tex b/introduction.tex  index 97fd386..9b85d66 100644  --- a/introduction.tex  +++ b/introduction.tex 
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g_{\alpha \beta}(\bf {r}) = \frac{\partial^2 {U} }{\partial \alpha \partial \beta} \;\;\;\;\; \alpha, \;\; \beta = x, y e z.  \end{equation}  formam a matriz de tensores gradientes de gravidade:  \Gamma (\bf r) =  \[ \left( \begin{array}{ccc} a g_xx  & b g_xy  & c g_xz  \\ d g_yx  & e g_yy  & f g_yz  \\ g g_zx  & h g_z_y  & i g_zz  \end{array} \right)\] \begin{equation}