I'm afraid it is. I had to relinquish my copies of Butcher's Copy Editing and the New Hart's Rules when I left my editorial job, but I've found the rule of inde

I'm afraid it is. I had to relinquish my copies of Butcher's Copy Editing and the New Hart's Rules when I left my editorial job, but I've found the rule of indefinite articles preceding vowels referenced on the Chicago Manual of Style site[0]. [0] http://www.chicagomanualofstyle.org/qanda/data/faq/topics/Usage/faq0068.html http://www.chicagomanualofstyle.org/qanda/data/faq/topics/Us...