For works written independently of the publisher, writers often first submit a query letter or proposal directly to a literary agent or to a publisher. Submissions sent directly to a publisher are referred to as unsolicited submissions, and the majority come from previously unpublished authors. If the publisher accepts unsolicited manuscripts, then the manuscript is placed in the slush pile, which publisher's readers sift through to identify manuscripts of sufficient quality or revenue potential to be referred to acquisitions editors for review. The acquisitions editors send their choices to the editorial staff. The time and number of people involved in the process is dependent on the size of the publishing company, with larger companies having more degrees of assessment between unsolicited submission and publication. Unsolicited submissions have a very low rate of acceptance, with some sources estimating that publishers ultimately choose about three out of every ten thousand unsolicited manuscripts they receive.