Referencing is one of the features specifically for use with pointers. The ampersand operator & is used for this purpose. If x is a variable, then &x represents the address of the variable x.
※ NOTES AND WARNINGS:
Pointers are one of the complicated subjects for beginners in learning C, and it is possible to write the vast majority of Arduino sketches without ever encountering pointers. However for manipulating certain data structures, the use of pointers can simplify the code, and knowledge of manipulating pointers is handy to have in one's toolkit.