Recipe books not dropping

I invested $510,000 in Cairo and $320,00 in Jaffa.  The Historical Crafts Guide was supposed to drop in Cairo at $400,000 investment and the Expert Craftsman's Training Book was supposed to drop in Jaffa at $300,000.  Neither happened.  Checked all the shops and it isn't available there either.  England is allied with Venice, so that isn't a factor.  What is up?