One of the best and most complete references is Safari Club International’s record book, available online (www.scirecordbook.org). It includes both pictures and descriptions of all African species. Various field guides to African animals are also available and are fun to actually take on your safari. However, do not expect that all animals taken will place high in any record book, and try not to establish pre-conceived “minimum standard” of horn length for the various species. Most areas produce better quality of one animal than another, and all any PH can do is attempt to find you animals that are of good quality for the area you are hunting.
Provided the hunter pays attention, shoots well, and has a bit of luck, most hunters’ animals at the end of the safari will follow a bell curve. Some trophies will be average, some will be very good, and a few will be exceptional. However, luck plays a factor in all hunting, so it is impossible to predict exactly which animals might be spectacular.