fixed links to sub-READMEs

README.md

@@ -23,14 +23,14 @@ you should read the per-type documentation.
 ## externals that can be simply build with `make`
 
 If your project uses a simple `make` based buildsystem
-(such as the one being based on [pd-lib-builder][]),
-please follow the instructions in [pd-lib-builder/README.md]
+(such as the one being based on `pd-lib-builder`),
+please follow the instructions in [pd-lib-builder/README.md](pd-lib-builder/README.md).
 
 ## externals that don't require any compilation
 
 If your project doesn't require *any* compilation
 (e.g. because it is an abstraction-only library),
-please follow the instructions in [no-build/README.md]
+please follow the instructions in [no-build/README.md](no-build/README.md).
 
 
 # what it does