demo code for using multiple PCD8544 ("Nokia 5110 displays") on one ESP8266
This code is an example how to use two Nokia displays from one ESP8266, some explainations on how to modify the code to make it usable for a third display are in the code as comments with some more sample code.
Thanks to this Adafruit forum thread: https://forums.adafruit.com/viewtopic.php?f=25&t=38893 with some sample code for the Arduino Uno