1) added papper "A Poor Man s Concurrency Monad" by Koen Claessen to the "haskell" section

2) added README for "pattern_matching" section"
3) added 📜 in readme to papers that hosts in the repo

haskell/README.md

@@ -1,5 +1,5 @@
 # Haskell
 
-
-* [Tackling the Awkward Squad: monadic input/output, concurrency, exceptions, and foreign-language calls in Haskell](../haskell/tackling-the-awkward-squad-monadic-input-output-concurrency-exceptions-and-foreign-language-calls-in-haskell.pdf) by Simon Peyton Jones
-* [Making a Fast Curry: Push/Enter vs. Eval/Apply for Higher-order Languages](../haskell/making-a-fast-curry-push-enter-versus-eval-apply-for-higher-order-languages.pdf) by Simon Marlow and Simon Peyton Jones. A classic... describes well the execution model GHC uses for Haskell, and catches the brilliant authors in a design pivot from original intuition to new conclusions based on empirical data.
+* :scroll: [Tackling the Awkward Squad: monadic input/output, concurrency, exceptions, and foreign-language calls in Haskell](../haskell/tackling-the-awkward-squad-monadic-input-output-concurrency-exceptions-and-foreign-language-calls-in-haskell.pdf) by Simon Peyton Jones
+* :scroll: [Making a Fast Curry: Push/Enter vs. Eval/Apply for Higher-order Languages](../haskell/making-a-fast-curry-push-enter-versus-eval-apply-for-higher-order-languages.pdf) by Simon Marlow and Simon Peyton Jones. A classic... describes well the execution model GHC uses for Haskell, and catches the brilliant authors in a design pivot from original intuition to new conclusions based on empirical data.
+* :scroll: [A Poor Man's Concurrency Monad](../haskell/a-poor-mans-concurrency-monad.pdf) by Koen Claessen. Paper describes how without adding any primitives to the language, you could define a concurrency monad transformer in Haskell.

pattern_matching/README.md

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+# Pattern Matching
+
+* :scroll: [Compiling Pattern Matching to good Decision Trees](../pattern_matching/compiling-pattern-matching-to-good-decision-trees.pdf) by Luc Maranget. Paper address the issue of compiling ML pattern matching to efficient decisions trees.
+* :scroll: [Extensible Pattern Matching in an Extensible Language](../pattern_matching/extensible-pattern-matching-extensible-language.pdf) by Sam Tobin-Hochstadt. Paper present a sophisticated pattern matcher for [Racket](http://racket-lang.org/), implemented as language extension using macros.
+* :scroll: [Warnings for pattern matching](../pattern_matching/warnings-for-pattern-matching.pdf) by Luc Maranget. Paper examine the ML pattern-matching anomalies of useless clauses and non-exhaustive matches.