Most of the sulfur occurs in tars, i.e., in the colloidally dissolved part. There are low-sulfur oils (S< 0.3%), medium-sulfur (5 > 1%), and high-sulfur oils (S > 4%), such as the Chusovoi, Termez, and Mexican oils. Nitrogen, like sulfur, is found ...
Mikhail Evgenʹevich Alʹtovskiĭ, 1961