Original sentence: Such a chain is a sequence of functions, say f1, f2, f3, etc, with the property that if we differentiate any of the functions in this chain then the result can be written in terms of the function itself and all the functions preceeding it in the chain (specifically as a polynomial in those functions and the variables involved)
Edited sentence: Such a chain is a sequence of functions, say f1, f2, f3, etc, with the property that if we differentiate any of the functions in this chain then the result can be written in terms of the function itself and all the functions preceding it in the chain (specifically as a polynomial in those functions and the variables involved)