Add some references to the README

README.md

@@ -14,3 +14,8 @@ A collection of CMake helper functions and tools that are common to all IHTA C++
   Primarily sets the output `bin` and `lib` directories so debugging works on windows builds.
 - `ihta_add_test`: Adds a unit test executable target including downloading the dependencies, CTest registration and optional code coverage.
 - `build_doc`: Builds doxygen documentation with nice styling.
+
+## References
+
+- [cpp_coverage](https://github.com/ekcoh/cpp-coverage/blob/master/cmake/cpp_coverage.cmake)
+- [crt_registertest](https://github.com/pthom/cmake_registertest/blob/master/src/crt_registertest.cmake)