Linked from
The 6 pages that link to Oil-drop experiment, each with the reason it gives.
Coulomb's lawRelated: The electrostatic force was calculated using Coulomb's law.
Stokes' lawBroader topic: Stokes' law helped infer droplet sizes and viscous drag.
Coulomb interactionRelated: Its force balance uses electrostatic forces to determine charge.
Robert MillikanBroader topic: Millikan used suspended droplets to determine the electron’s charge.