father(john,sister(Amy))=father(X,sister(mary))
si con {Amy/mary,X/john}

[f(a),f(1),g(2)]=[H|T]
si con {H/f(a),T/[f(1),g(2)]}

[f(a),f(1),g(Y)]=[f(X)|T]
si con {X/a,T/[f(1),g(Y)]}

parent(a,B,c)=parent(A,b,C)
si con {A/a,B/b,C/c}

Father=father(john)
si con {Father/father(john)}

parent(a,b)=parent(a,b,c)
no
