1:

  R* trees sometimes fail their self-tests, with an error message of
  the form

    There is no applicable method for the generic function
      #<STANDARD-GENERIC-FUNCTION (SETF PARENT) (1)>
    when called with arguments
      (#<SPATIAL-TREE-NODE #<(0.01974988,0.5777439) - (0.58179224,1.8144482)>
          (# # #)>
       #S(LEAF-NODE-ENTRY
          :RECTANGLE #<(0.373667,0.62124753) - (0.58179224,1.5787126)>
          :DATUM #<(0.373667,0.62124753) - (0.58179224,1.5787126)>)).
