Pretty much as noc said. Taking clones is not reccommended during flowering not because it can't be done, but because of the extended time u'll spend waiting for them to take root as clones taken from flowering plants WILL take longer.
so wher is the link to said respected grower i say he or she is wrongi beg to differ. I red from a highly respective grower that cloneing 21 days into flowering had the best results. Sure they root a lil slower but the yield is suppose to be that much bigger. If i remember correctly he said somthing about because your cutting from a mature plant. Im not claiming to be a expert im just sharing what i have red. Hope this helps. peace.