Add some links

Author: tfausak

content/issues/139.markdown

@@ -16,7 +16,23 @@ undefined
 
 ## In brief
 
-undefined
+-   [Abstraction levels in functional programming](https://tzemanovic.gitlab.io/posts/abstraction-levels-in-functional-programming/)
+-   [Advent of Haskell](https://medium.com/@mvaldesdeleon/advent-of-haskell-950d6408a729)
+-   [Balancing scans](https://doisinkidney.com/posts/2018-12-21-balancing-scans.html)
+-   [Compiling to categories 3: A bit cuter](http://www.philipzucker.com/compiling-to-categories-3-a-bit-cuter/)
+-   [Curses Pac-man game in Haskell](https://github.com/ajkavanagh/pacman/tree/b72468ed0519858288f35f1ae1b2cfb91516df4f)
+-   [Fluent polymorphism with visible type applications](https://blog.sumtypeofway.com/fluent-polymorphism-with-visible-type-applications/)
+-   [Graphs are to categories as lists are to monoids](https://alhassy.github.io/PathCat/)
+-   [Happy Haskell Programming for GHC 8.x](http://haskell.1045720.n5.nabble.com/Happy-Haskell-Programming-for-GHC-8-x-td5888460.html)
+-   [Open Season on Hylomorphisms](https://bartoszmilewski.com/2018/12/20/open-season-on-hylomorphisms/)
+-   [PureScript series now available](https://mmhaskell.com/blog/2018/12/24/purescript-series-now-available)
+-   [Rigid types and block arguments](https://typeclasses.com/news/2018-12-yearly-billing-regional-discounts)
+-   [Solving planning problems with Fast Downward and Haskell](https://ocharles.org.uk/blog/posts/2018-12-25-fast-downward.html)
+-   [Stackage LTS 13 with ghc-8.6.3](https://www.stackage.org/blog/2018/12/announce-lts-13)
+-   [Testing `distributed-process` apps using Hspec](https://filib.io/posts/2018-12-24-testing-distributed-process-apps-with-hspec.html)
+-   [Welcome to GitLab!](https://mail.haskell.org/pipermail/ghc-devs/2018-December/016716.html)
+-   [Xiaolin Wu’s fast antialiased line drawing algorithm in Haskell](https://blog.rcook.org/blog/2018/xiaolin-wu-algorithm/)
+-   [ZuriHac 2019 registration](https://zfoh.ch/zurihac2019/#registration)
 
 ## Package of the week