I have the (matrix representation of the) Heisenberg group modulo 3.
$$\begin{pmatrix} 1 & a & b\\ 0 & 1 & c \\ 0 & 0 & 1 \end{pmatrix}: a, b, c \in \mathbb{Z}/3\mathbb{Z}$$
On this Wikipedia article, it is denoted $H$ generally, although that could be for any Heisenberg group. It seems to suggest $H_3(\mathbb{Z}/3\mathbb{Z})$ or even just $H_3$, (although I might be misreading this). $H_3$ is also used for a Coxeter group according to this.
This reference uses $\text{Heis}(\mathbb{Z}/3\mathbb{Z})$.
Is there a standard peice of notation I should use, or something that'd generally be unambiguous in meaning?