D10 Tree Study I, Tate, London (T09307)
D11 Tree Study II, Tate, London (T09310)
D12 Tree Study III, Tate, London (T09308)
D13 Tree Study IV, Tate, London (T09311)
D388 Trtee Study The National Library of Wales, Aberystwyth / Llyfrgell Genedlaethol Cymru