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has witnessed was witnessed witnessed is witnessed
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benefit; discovered have benefited; was discovered have benefited; discovered benefit; was discovering
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at the beginning of the nineteenth century in the middle of the nineteenth century more than two hundred years ago when people first sent letters and postcards.
to introduce introduce being introduced to be introduced
stylistic great personal exclusive
eighteen eighteenth nineteen nineteenth
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before the Middle Ages about in the nineteenth century in Greece or Rome machines to take tests
The twenties. The thirties. The forties. The fifties.
at the beginning of nineteenth century at the beginning of twentieth century before the nineteenth-century after World War I
personal efficient consistent practical
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