Linked from
The 21 pages that link to Electronic oscillator, each with the reason it gives.
Quartz clockNarrower topic: A quartz clock is a specialized oscillator-based timekeeping system.
Phase-locked loopNarrower topic: The loop’s adjustable signal source is an oscillator.
ClockNarrower topic: Regular oscillation supplies the repeating signal that many clocks count.
SynchronizationNarrower topic: Oscillators provide the recurring cycles that synchronization aligns.