macuser is absolutely right. In addition to Pub 17, pg 29 <a rel="nofollow" target="_blank" href="
https://www.irs.gov/pub/irs-pdf/p17.pdf">https://www.irs.gov/pub/irs-pdf/p17.pdf</a> , the rule is also referenced in Pub 501, page 14. <a rel="nofollow" target="_blank" href="
https://www.irs.gov/pub/irs-pdf/p501.pdf">https://www.irs.gov/pub/irs-pdf/p501.pdf</a>
