Hermite normal forms and $\delta$-vector

Let $\delta(\Pc) = (\delta_0, \delta_1,..., \delta_d)$ be the $\delta$-vector of an integral polytope $\Pc \subset \RR^N$ of dimension $d$. Following the previous work of characterizing the $\delta$-vectors with $\sum_{i=0}^d \delta_i \leq 3$, the possible $\delta$-vectors with $\sum_{i=0}^d \delta_i = 4$ will be classified. And each possible $\delta$-vectors can be obtained by simplices. We get this result by studying the problem of classifying the possible integral simplices with a given $\delta$-vector $(\delta_0, \delta_1,..., \delta_d)$, where $\sum_{i=0}^d \delta_i \leq 4$, by means of Hermite normal forms of square matrices.