If you are deleting entire sentences of a paragraph before continuing a quotation, add one additional period and place the ellipsis after the last word you are quoting, so that you have four in all if you are deleting the end of a quoted sentence, or:
In the event that you begin your quotation of an author in the center of a sentence, you want not indicate deleted words with an ellipsis. Be certain, however, that the syntax of the quotation fits smoothly aided by the syntax of one’s sentence:
Reading “is a noble exercise,” writes Henry David Thoreau.
Use square brackets when you need to add or substitute words in a quoted sentence. The brackets indicate to your reader a word or phrase that will not come in the original passage but that you’ve got inserted in order to prevent confusion. As an example, when a pronoun’s antecedent will be unclear to readers, delete the pronoun from the sentence and substitute an word that is identifying phrase in brackets.