The ITF publishes the 2017 ranking, World Team and tournament regulations for seniors on an annual basis. Here is the link to the 2017 regulations, 117 pages (including appendices).
This handbook describes rules for running the ITF World Championships, World Team Championships and circuit events, including the number of seeds, when the schedule of play should be posted, the number of matches per day and rest periods and more.
The online PDF of the 2017 Seniors Regulations can be found here: http://www.itftennis.com/media/252047/252047.pdf