Re: Simple enough for every reader?

On 07.07.2025 10:29, Mikko wrote:
 

Bijection requires completeness of domain and codomain.

 So you say but cannot prove.

 It is so by definition. See e.g. W. Mückenheim: "Mathematik für die ersten Semester", 4th ed., De Gruyter, Berlin (2015).

 Can you refer to some better author?

 That is hardly feasible. But you can look up the definition in every textbook of your choice. You will find the same result. Even Wikipedia will be sufficient: a bijection is a relation between two sets such that each element of either set is paired with exactly one element of the other set.