Marc Evans is possibly the first person who referred to themselves as a triathlon coach, as opposed to a swim or run coach that helped triathletes. Marc Evans wrote a number of books about training for endurance events back in the 1980’s and 90’s and was in fact one of the first resources I purchased for my coaching business when I first started it back then. Endurance Athlete’s Edge is still a great resource. He takes a traditional approach to periodisation with five phases.