After injecting small groups of people, Salk announced in October 1953 that he had injected 600 people with the vaccine.
(Salk; announced; T:in October 1953; that he had injected 600 people with the vaccine; T:After injecting small groups of people) Context(Salk announced,List([40, 54))):(he; had injected; 600 people; with the vaccine)
Salk announced,List([40, 54))
Salk he
announced had injected
T:in October 1953 that he had injected 600 people with the vaccine T:After injecting small groups of people
600 people with the vaccine