private Item nextToCatalogue() {
    float quality = Float.POSITIVE_INFINITY ;
    Item catalogued = null ;
    for (Item i : stocks.matches(DATALINKS)) {
      if (! (i.refers instanceof Skill)) continue ;
      if (i.quality < quality) { catalogued = i ; quality = i.quality ; }
    }
    if (catalogued == null || catalogued.quality >= 5) return null ;
    return catalogued ;
  }