Papers and publications within the social sciences, business and nursing typically use APA documentation format to acknowledge sources. As explained in the sixth edition of the "Publication Manual of the American Psychological Association," quoted material should appear exactly as it does in the original, but you may choose to omit unnecessary ideas from a quote. Doing so requires careful punctuation and structure to avoid improper use of quotations.
Ellipses are a series of periods with spaces between them that indicate information has been left out of a quote. Three dots mean that at least one word is missing. For instance, the original quote, "The boy in the blue suit went home," could be shortened like this: "The boy . . . went home." If your omission crosses end punctuation, use four dots in the ellipses -- one to indicate the period at the end of the first sentence you quoted and three for the omission. Do not use ellipses at the start or end of a sentence unless you need to emphasize that you are quoting from the middle of the sentence.
Writers must be careful to retain the original intention when leaving out information from quotes. If adding ellipses affects the grammar or other structure of your sentence so it might confuse your reader, add words in square brackets for clarification. For example, if you mention several men and then use the pronoun "he" in a quote, you may need to clarify if you omit part of the quote, as in this example: "He [Bartholomew] instigated the change."