The Duras theme is when a bishop of the "wrong" color with a pawn on the a- or h-file succeeds to win.

5.1 Created by Lewis Stiller

3.02 Created by Peter Boll.

CQL 5.1
; White wins with a or h pawn and bishop on the "wrong color" cql(input heijden.pgn result 1-0) P on a2-6 or h2-6 B on darksquares power 4 A power 0 a

CQL 3.02
; Duras.cql
; Duras Theme = When a wrong colored bishop with a- or h-pawn manages to win. ; This cql only searches for a mainlines where at the end there is the wrong coloured bishop with an a- or h- pawn and max one black pawn. ; This cql can be extended by searching for more pawns on the a- or h-file and searching in variations. (match
:pgn heijden.pgn
:output Duras.pgn
:result 1-0 (position
; :variations
:piececount P 1 :piececount p 0 1
:piececount [QqRrNn] 0
:piececount B 1
:piececount P[a2-7] 1
B[a1,a3,a5,a7,b2,b4,b6,b8,c1,c3,c5,c7,d2,d4,d6,d8,e1,e3,e5,e7,f2,f4,f6,f8,g1,g3,g5,g7,h2,h4,h6,h8] 1) ; Bishop on black squares
:piececount P[h2-7] 1
B[a2,a4,a6,a8,b1,b3,b5,b7,c2,c4,c6,c8,d1,d3,d5,d7,e2,e4,e6,e8,f1,f3,f5,f7,g2,g4,g6,g8,h1,h3,h5,h7] 1)  ; Bishop on white squares
After executing this with "> cql Duras.cql" there are 223 studies found in the Harold van der Heijden Database V 2015.

Only 9 studies are presented here as examples: