$\forall$$g$, $h$:GrpSig\{i\}, $k$:GrpSig\{k\}, $r$:($\mid$$g$$\mid\rightarrow\mid$$h$$\mid$), $s$:($\mid$$h$$\mid\rightarrow\mid$$k$$\mid$).
\\[0ex]IsMonHom\{$g$,$h$\}($r$) $\Rightarrow$ IsMonHom\{$h$,$k$\}($s$) $\Rightarrow$ IsMonHom\{$g$,$k$\}($s$ o $r$)