Can't join different values to the same path

[nahueld]

I'm struggling to find a way to do the following:
var firebaseRef = new Firebase(url); var norm = new Firebase.util.NormalizedCollection( firebaseRef.child("/billing"), [firebaseRef.child("/people"),"people1","billing.buyer"], [firebaseRef.child("/people"),"people2","billing.seller"]) .select("billing.creationDate","billing.buyer", "billing.seller",{key:"people1.$value",alias:"buyerDetails"},{key:"people2.$value",alias:"sellerDetails"}); return norm.ref();

This cause a duplicate path error...

Notice that the objective of this is to use the same path to obtain buyer and seller rather than to have different endpoints for this.