Hard to read and even to understand ;
https://eml.berkeley.edu/~groland/pubs/vietnam-bombs_19oct05.pdf
https://vietnamembassy-usa.org/relations/us-veterans-help-land-mine-removal-vietnam#:~:text=During the war%2C U.S. forces,remain buried in the countryside.
There is another one; And not resolved yet after 50 years..
It is estimated that some 800 thousand tons of bombs and mines are still buried after the war conflicts in Vietnam.