The photographic library of 12 categories is for the benefit of showing you that portraits vary so much. To draw from life is the best way but sometimes when you are starting off as a newcomer to drawing it is easier to look at something that has been made before.  That is also why I have put together numerous variations of artwork from my students both children and adults for you to study and if inclined to make similar drawings.  There are too quite a few photographs of my own work that have been made over the last two decades.  The necklines (2000) the head studies (2016) and the skulls (2020).  You are more than welcome to make drawings by referring to these as well.