It might be every 10 years.
Every 4 years.
every 4 years
Leap years occur every 4 years.
Every four years.
About every 2 years.
each census is taken every 10 years
every 2 years
30
Every three years
100 every 2 years.
2 years after every winter olympics.
Many sources agree that pet scans are effective in finding cancer. These scans are said to help determine the location of tumors and whether or not they have spread.