PREFIX gbol: <http://gbol.life/0.1/>
select distinct ?fwd ?rev ?fragment
where {
    ?sample gbol:PCRPrimers ?primers .
    ?primers gbol:forwardPrimer/gbol:sequence ?fwd .
    ?primers gbol:reversePrimer/gbol:sequence ?rev .
    ?ngtax a <http://semantics.systemsbiology.nl/0.1/NGTax> .
    ?ngtax gbol:subFragment ?fragment .
    ?library a gbol:Library .
    ?library gbol:provenance/gbol:annotation ?ngtax .
    ?library gbol:sample ?sample .
}