Inclusion of shapes

Something is still unclear when reading ShEx documents.
What is the proper inclusion mechanism between these shapes :

Start=<XXX>
<XXX> & <ToBeIncluded>{
}

<ToBeIncluded>{
   :p2 xsd:string
}

and those shapes:

Start=<XXX>
<XXX> {
    & <ToBeIncluded>,
   :p rdf:Resource
}

<ToBeIncluded>{
   :p2 xsd:string
}


Any help is welcome.