found: The process photogram and illustrator, July 1900, via Google Books, July 30, 2015:page 112 ("The partnership heretofore existing between Emery Walker and Walter Boutall, trading as Walker & Boutall, photo-engravers, Clifford's Inn and Hammersmith, has been dissolved as from June 30th. The business of Walker & Boutall will be continued by Mr. Emery Walker. We understand that Mr. Boutall will continue his connection with photo-engraving business as chairman of Vaus & Crampton, Ltd.")
found: Oxford Dictionary of National Biography (WWW), July 30, 2015:(under Walker, Sir Emery, 1851-1933: in 1886, in partnership with Walter Boutall, Emery Walker founded the firm of "process and general engravers, draughtsmen, map-constructors, and photographers of works of art" known first as Walker and Boutall, later as Walker and Cockerell, and finally as Emery Walker, Ltd.)
