The book of the feet: a history of boots and shoes by Hall (1847)

Hall, J. S.; The book of the feet: a history of boots and shoes, William Graham, New York (1847)
URL (Google Books)

Essai sur l'histoire du parchemin et du vélin par Peignot (1812)

Peignot, Gabriel; Essai sur l'histoire du parchemin et du vélin, Paris (1812)
URL (Internet Archive)

"The chemical degradation of leather" by Larsen (2008)

Larsen, R.; " The chemical degradation of leather", CHIMIA International Journal for Chemistry 62 (11) (2008) 899-902

DOI: 10.2533/chimia.2008.899 (restricted access)

Abstract:

The chemical deterioration of vegetable tanned leather is caused by acid hydrolysis and oxidation due to environmental deteriorative factors like air pollutants, heat and light. In addition, the type of tannin material influences the rate of deterioration. The degree of deterioration can be measured by the fall in the shrinkage temperature (Ts) of the leather. New analysis of data shows that, although environmental factors have a generally larger influence on the deterioration, the average degree of oxidation is greater in older leathers and it significantly influences the Ts in these materials. Moreover, it is also shown that acid pollution is indicated in the relation between pH and the sulphate content measured in the leathers although ammonia is released by oxidation of amino acids and may influence the pH value in acid-damaged leathers.