The 63-Day Cycle in Maya Culture: Discovery of a New Calendric Factor (2016), Guillermo Bernal Romero

https://www.academia.edu/31163433/The_63_Day_Cycle_in_Maya_Culture_Discovery_of_a_New_Calendric_Factor_2016_?rhid=29657405257&swp=rr-rw-wc-4068972