John Ruskin (1854). “On the nature of Gothic architecture: and herein of the true functions of the workman in art. Being the greater part of the 6th chapter of the 2nd vol. of 'Stones of Venice'. [48 p.].”, p.18
John Ruskin “The stones of Venice (cont'd) Seven lamps of architecture. Lectures on architecture and painting, delivered at Edinburgh in Nov. 1853. An inquiry into some of the conditions at present affecting the study of architecture in our schools”
John Ruskin (1854). “On the nature of Gothic architecture: and herein of the true functions of the workman in art. Being the greater part of the 6th chapter of the 2nd vol. of 'Stones of Venice'. [48 p.].”, p.14