Deductions & credits

Just curious if there is an IRS document I can skim to help verify that a 'normal' 501c gift is not included as income?  I was alerted to Publication 3833 (Rev. 12-2014) (irs.gov) concerning 501c3 gifts received for disaster relief, but I can't see how it addresses gifts that were never intended to be considered disaster relief.  Can't gifts be received for other than disaster relief?  

Thanks!