Luis Vives – taxonomy – nivel query
$niveles = array( 'relation' => 'AND', array( 'taxonomy' => 'nivel', 'terms' => 'primaria', 'field' => 'slug', 'operator' => 'IN', 'include_children' => false, ), array( 'taxonomy' => 'nivel', 'terms' => 'secundaria', 'field' => 'slug', 'operator' => 'IN', 'include_children' => false, ), );