Refine wording

concurrency-primer.tex

@@ -690,7 +690,7 @@ \section{Concurrency tools and synchronization mechanisms}
 Consequently, we should not focus on comparing which communication tools or synchronization mechanisms are better, 
 but rather on exploring how to effectively use these tools in a given scenario to facilitate smooth communication between threads and achieve the programmer's goals.
 
-\section{Lock free}
+\section{Lock-free}
 In \secref{concurrency-tool}, we explored different mechanisms based on the characteristics of concurrency tools, 
 as described in \secref{atomicity} and \secref{rmw}.
 In this section, we need to explore which strategies can help programmers to design a concurrency program