1. http://www.ehow.com/info_8439501_effects-bubble-gum-environment.html#ixzz2sPMFrWri.
2. Butyl Rubber A new Hydrocarbon Product
3. Die Hochmolekularen Organischen Verbindungen Kautschuk and Cellulose (High Molecular Organic Compounds, Rubber and Cellulose);Staudinger,1932
4. H.L. Fisher, R.H. Gerke, in: C.C. Davis, J.T. Blake (Eds.), The Chemistry and Technology of Rubber, ACS Manograph Series No. 74, 1937, ACS, Washington, DC, USA, p. 126.