The book refers to Chebyshev as "Chebychev" which is apparently a [common error](https://en.wikipedia.org/wiki/Pafnuty_Chebyshev#:~:text=Chebychev%20is%20an%20erroneous%20mixture%20between%20English%20and%20French%20transliterations%2E).
The book refers to Chebyshev as "Chebychev" which is apparently a common error.