query: SELECT ?item ?catcode ?catletter ?catnum WHERE { 
  ?item p:P528 [ pq:P972 wd:Q86600002 ; ps:P528 ?catcode].  
  BIND( xsd:integer(REPLACE(?catcode, "[a-zA-Z]", "")) AS ?catnum) .
  BIND(REPLACE(?catcode, "[0-9]*", "") AS ?catletter) .
  } ORDER BY ?catletter ?catnum