Which happened after the first traffic signal was set up in London?

It exploded less than a month after it was implemented, injuring its policeman operator.

Explanation:

dr. kings dream speech

explanation:

it was late in the day and hot, and after a long march and an afternoon of speeches about federal legislation, unemployment and racial and social justice, the rev. dr. martin luther king jr. finally stepped to the lectern, in front of the lincoln memorial, to address the crowd of 250,000 gathered on the national mall.

- "the basic difference between keywords and subjects is that subjects (or "subject headings") have been predetermined, while keywords have not. a keyword is an easy place to start because you can use any word that seems to fit your search; this is called "natural language" searching."