Removed <br/> in comment in part13.rs.
//@ pitfall of concurrent programming: data races. We will see how that works concretely.
// Before we come to the actual code, we define a data-structure `Options` to store all the information we need
-// to complete the job: Which files to work on, which pattern to look for, and how to output. <br/>
+// to complete the job: Which files to work on, which pattern to look for, and how to output.
//@ Besides just printing all the matching lines, we will also offer to count them, or alternatively to sort them.
#[derive(Clone,Copy)]
pub enum OutputMode {