File:CD drive DC 5 V 2-phase 4-wire Stepper motor with Leadscrew - (2).jpg - Wikimedia Commons
Difference Between 4-Wire, 6-Wire and 8-Wire Stepper Motors - NI
Difference Between 4-Wire, 6-Wire and 8-Wire Stepper Motors - NI
Walfront 2 Phase 4 Wire Stepper Motor Driver DC10V to 26V 2 in 1 Bipolar Stepper Motor Drivers Wiring Photoelectric Isolation for 2 Phase Micro Stepping Motors: Amazon.com: Industrial & Scientific
Controlling Stepper Motors Using Power IO Wildcard, C Library Functions and MOSFET Drivers for Four-phase Six-wire Unipolar Permanent-magnet Stepper Motor
How to connect a stepper motor with exactly 4 wires to Arduino? - Electrical Engineering Stack Exchange