Answer:
The use of the calendar
Explanation:
They all used the calendar to predict eclipses, schedule religious ceremonies, and determine when to plant/harvest crops, and go off to war.
China--Nixon recognized Communist China and was the first president to visit the country. He also began trade talks regarding China.
Vietnam--Nixon pulled out ground troops and created a peace agreement to end US involvement in Vietnam.
Nixon created the EPA which provided federal funding to protect the environment and create industry regulations on companies.
Please post a picture of the map
