An html version of knightchase.cql. Created by Gady Costeff and Lewis Stiller.

;Search for positions in which a knight chases a  knight of another color, continually offering to sacrifice itself
 :pgn heijden.pgn
 :output knightchase.pgn
 :forany chaser [nN]  ; this is the chasing knight
 :forany chasee [Nn]  ; this is the chased knight
  :tagmatch chaser n ; make sure the chaser is really a black knight, 
                     ;not a N or a pawn that will promote to one
  :tagmatch chasee N ; make sure the chasee is really a white knight, 
                     ; and not a n or a pawn that will promote to one
	   :sequence ((position :wtm :attackcount $chaser $chasee 1 :movefrom $chasee) 
		      (position :movefrom $chaser)
                      (position :attackcount $chaser $chasee 1))
	   :matchcount 4 100

After executing this with "> cql KnightChase.cql" there are 23 studies found in the Harold van der Heijden Database V 2015.
NB. When you see {MATCH} in the text, it means that cql has found the position asked for.

Below only 5 studies are presented: