Added reference to scientific paper

README.md

@@ -9,6 +9,12 @@ Its main particularity compared to conventional Minetest mapgens is that rivers
 
 It used to be composed of a Python script doing pre-generation, and a Lua mod reading the pre-generation output and generating the map. The code has been rewritten in full Lua for version 1.0 (July 2021), and is now usable out-of-the-box as any other Minetest mod.
 
+# Author and license
+License: GNU LGPLv3.0
+
+Code: Gaël de Sailly
+Flow routing algorithm concept (in `terrainlib/rivermapper.lua`): Cordonnier, G., Bovy, B., & Braun, J. (2019). A versatile, linear complexity algorithm for flow routing in topographies with depressions. Earth Surface Dynamics, 7(2), 549-562.
+
 # Requirements
 Mod dependencies: `default` required, and [`biomegen`](https://github.com/Gael-de-Sailly/biomegen) optional (provides biome system).
 

terrainlib_lua/rivermapper.lua

@@ -1,5 +1,17 @@
 -- rivermapper.lua
 
+-- This file provide functions to construct the river tree from an elevation model.
+-- Based on a research paper:
+--
+--     Cordonnier, G., Bovy, B., and Braun, J.:
+--     A versatile, linear complexity algorithm for flow routing in topographies with depressions,
+--     Earth Surf. Dynam., 7, 549–562, https://doi.org/10.5194/esurf-7-549-2019, 2019.
+--
+-- Big thanks to them for releasing this paper under a free license ! :)
+
+-- The algorithm here makes use of most of the paper's concepts, including the Planar Boruvka algorithm.
+-- Only flow_local and accumulate_flow are custom algorithms.
+
 local function flow_local_semirandom(plist)
 	local sum = 0
 	for i=1, #plist do