University Mathematics Handbook (2015)
XII. Complex Functions
Chapter 8. Behavior of Analytical Functions at Infinity
a. Point is said to belong to – neighborhood of if belongs to - neighborhood of .
b. Function is analytic in the neighborhood of , if function is analytic in the neighborhood of .
c. is a removable singular point, a pole or an essential singular point of function if is a removable singular point, a pole or an essential singular point of function , respectively.