https://www.academia.edu/2401443/_The_Norman_invasion_of_Sicily_1061-1072_Numbers_and_Military_Tactics_War_in_History_17_2010_pp._381-402
nice find David and this is your thing then I heartily recommend John Julius Norwich's 'The Kingdom in the The Sun'
Thank Holly. I have it :)
one of the best history books I have read in a long while possibly only rivalled by his Byzantine trilogy