[SOLVED] Second Fundamental Form

Hi there. I'm trying to understand the Second Fundamental Form but I'm stuck on something. Let:

$\displaystyle \textbf{X}=(x(u^1,u^2),y(u^1,u^2),z(u^1,u^2))$ is a parameterised form of a surface.

$\displaystyle \textbf{X}_i=\dfrac{\partial \textbf{X}}{\partial u^i}$

$\displaystyle \textbf{X}_{i j}=\dfrac{\partial \textbf{X}^2}{\partial u^i \partial u^j}$

It's written $\displaystyle \textbf{X}_{i j}=\Gamma_{ij}^{r}\textbf{X}_r +L_{ij}\textbf{U}$ where $\displaystyle \textbf{U}$ is the normal vector to the surface.

I don't understand what is $\displaystyle L$ and $\displaystyle \Gamma$