(let ((isa-base (make-hash-table :size 20))
      (includes-base (make-hash-table :size 20))
      (article-base (make-hash-table :size 20)) )
  (defun set-isa (x y) (setf (gethash x isa-base) y))
  (defun get-isa (x) (gethash x isa-base))
  (defun set-includes (x y)
    (setf (gethash x includes-base) y) )
  (defun get-includes (x) (gethash x includes-base))
  (defun set-article (x article)
    (setf (gethash x article-base) article) )
  (defun get-article (x) (gethash x article-base))
 )