What is the order of events Salk needed to follow to discover his polio vaccine?​

Explanation:

polio vaccine was discovered by jonas saulk, 1953. order of events he had to follow / Saulk introduced the 1st vaccine with dead polio virus injected in humans, in 1953. 1st 2 introduce dead virus into humans, proved to be a substantial tool for vaccination of children and adults. proven to work, we use this vaccine today...

to eliminate ambiguous remote or broad reference it is necessary to focus on anaphoric reference. by definition "anaphoric reference means that a word in a text refers back to other ideas in the text for its meaning." the references should be clear and leave no room for ambiguity.

in the first case the pronoun it probably refers to the car but it has not been mentioned before so we should replace it for the car. in doing so the statement becomes clear.

in sentence number   two   the pronoun he refers to charles dickens the author. yet, the first half of the sentence is about the book a tale of two cities. to repair this it would be better to rephrase the first half : after i read   a tale of two cities by dickens, he so as to remove the remote reference.