Please, please, please for the love of all that is righteous and legitimate (even some illegitimate things–they deserve love, too, right?) stop putting periods on the outside of quotation marks, be they single or double.
Correct: She murmured aloud, as she walked through the park, past the sleeping man, “If I can’t trust the system, he doesn’t stand to gain anything from it.”
Incorrect: I agree with Harriet Ann Jacobs’ sentiment that “There are wrongs which even the grave does not bury”.
Harriet Jacobs, by the way, is author of “Incidents of a Slave Girl”–one of the few autobiographical narratives about slavery written by a woman.