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A section of a group $G$ is a quotient of a subgroup of $G$ That is, a section of $G$ is a group of the form $H/N$ where $H$ is a subgroup of $G$ and $N$ is a normal subgroup of $H$
A group $G$ is said to be involved in a group $K$ if $G$ is isomorphic to a section of $K$
The relation `is involved in' is transitive, that is, if $G$ is involved in $K$ and $K$ is involved in $L$ then $G$ is involved in $L$
Intuitively, `$G$ is involved in $K$ means that all of the structure of $G$ can be found inside $K$
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