How to untag, in an XML file, a chain of tagged characters that are embedded within specified tags

What is the xmlstarlet command to untag, in an XML file, a chain of tagged characters that are embedded within specified tags? Example: searching every occurrence of the tag , that needs to be deleted only if it is within the ... tag: * Input example:

This is an example. This is a test;

* Desired output:

This is an example. This is a test;

For the sake of generalization, I am keeping the second sentence in the example, i.e.

This is a test;

but if it is an issue, it can be ignored.