Chapter: Equivalent Models of Computation: Wrong Hyperlink

[mzhao80]

Chapter name: Equivalent Models of Computation

List of bugs/typos

1. Subsection: Formal definition of the $\lambda$ calculus: Link for Chelsea Voss's diagram is incorrect, as it goes to someone else's website entirely (John Tromp); I could not find the correct source (it has probably been taken down) but the most appropriate link would be her related talk at https://www.deconstructconf.com/2017/chelsea-voss-programming-languages-as-notations.
2. Section: From enhanced to pure $\lambda$ calculus: Throughout this section, the FILTER function is not mentioned despite being introduced as part of the enhanced lambda calculus earlier.