Add DOIs and preprints for cited papers.

docs/overview.md

@@ -18,27 +18,34 @@ the following tools:
 
 - `klocalizer` takes the name of a compilation unit and automatically
   generates a `.config` file that, when compiled, will include the
-  given compilation unit.  It uses the logical models from `kclause` and `kmax`
+  given compilation unit.  It uses the logical models from `kclause`
+  and `kmax`.  The configuration localization problem is described in
+  an [SPLC 2018 challenge
+  paper](https://doi.org/10.1145/3233027.3236404)
+  ([preprint](https://paulgazzillo.com/papers/splc18challenge.pdf)).
 - `kclause` "compiles"
   [Kconfig](https://www.kernel.org/doc/html/latest/kbuild/kconfig-language.html)
   constraints into logical formulas.  `kextractor` uses Linux's own
   Kconfig parser to perform an extraction of the syntax of
   configuration option names, types, dependencies, etc.  It is
   described in our [ESEC/FSE 2021 research
-  paper](https://paulgazzillo.com/papers/esecfse21.pdf).
+  paper](https://doi.org/10.1145/3468264.3468578)
+  ([preprint](https://paulgazzillo.com/papers/esecfse21.pdf)).
 - `kmax` collects configuration information from [Kbuild
   Makefiles](https://www.kernel.org/doc/html/latest/kbuild/makefiles.html).
   It determines, for each compilation unit, a symbolic Boolean
   expression that represents the conditions under which the file gets
   compiled and linked into the final program.  Its algorithm is
   described in our [ESEC/FSE 2017 research
-  paper](https://paulgazzillo.com/papers/esecfse17.pdf) and the
+  paper](https://doi.org/10.1145/3106237.3106283)
+  ([preprint](https://paulgazzillo.com/papers/esecfse17.pdf)) and the
   original implementation is in [version
   1.0](https://github.com/paulgazz/kmax/releases/tag/v1.0).
 - `kismet` does verification-based static analysis to find unmet
   dependency bugs and generates test cases.  It is described in our
   [ESEC/FSE 2021 research
-  paper](https://paulgazzillo.com/papers/esecfse21.pdf).
+  paper](https://doi.org/10.1145/3468264.3468578)
+  ([preprint](https://paulgazzillo.com/papers/esecfse21.pdf)).
 
 ## Contributors