Linked from
The 63 pages that link to Beta decay, each with the reason it gives.
TritiumNarrower topic: Tritium decays by emitting an electron as one neutron becomes a proton.
Chien-Shiung WuNarrower topic: The cobalt-60 nuclei in Wu’s test decayed by emitting beta particles.
Rubidium-87Narrower topic: Rubidium-87 decays by beta-minus emission, becoming strontium-87.
Free neutron decayNarrower topic: Free neutron decay is beta-minus decay without a nucleus.