Search for "author:(Wheatley, Phillis, 1753-1784) title:(Poems on various subjects, religious and moral. /)" found nothing
Try limiting your search to just one of these... author:(Wheatley, or Phillis, or 1753-1784) or title:(Poems or on or various or subjects, or religious or and or moral. or /)
Try the "More search options" page.