PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#> 
PREFIX ex: <http://keg.vse.cz/patomat/function#>
SELECT ?c1 ?c2 ?p
WHERE {
?c1 rdfs:subClassOf ?p.
?c2 rdfs:subClassOf ?p.
FILTER 
(
?c1!=?c2 &&
ex:headNounEquality(?c1,?c2) &&
!ex:headNounEquality(?c1,?p)
)
}