Consider the four non-degenerate symmetric bilinear forms over $\mathbb{Q}$ given be the matrices $\bigl(\begin{smallmatrix} 1&0\\ 0&1 \end{smallmatrix} \bigr)$,$\bigl(\begin{smallmatrix} 1&0\\ 0&-1 \end{smallmatrix} \bigr)$,$\bigl(\begin{smallmatrix} -1&0\\ 0&1 \end{smallmatrix} \bigr)$ and $\bigl(\begin{smallmatrix} -1&0\\ 0&-1 \end{smallmatrix} \bigr)$. Considered over $\mathbb{Z}$ these matrices become unimodular symmetric bilinear forms.
I want to classify all unimodular symmetric bilinear forms over $\mathbb{Z}$, which are, considered over $\mathbb{Q}$ equivalent to one of the given forms above.
Can somebody help me?