Memorandum 23 April 1811 Wellington to Beresford
Dispatches 1844 edition Volume 4
See pages 763-766
https://books.google.ca/books?id=QjXSAAAAMAAJ&printsec=frontcover&dq=
Beresford to Wellington 15 May 1811
Supplementary Despatches Volume 7
See pages 125-126