update README after preparing release and publication on Zenodo.

README.md

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+[![DOI](https://zenodo.org/badge/302602074.svg)](https://zenodo.org/doi/10.5281/zenodo.4134626)
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 # PSD Analysis using Machine Learning to identify hydraulic conductivity
 
-This repository provides routines to perform particle size distribution (PSD) analysis, particularly workflows to estimate hydraulic conductivity with six Machine Learning (ML) algorithms:
+This repository accompanies the manuscript "Predicting Saturated Hydraulic Conductivity from Particle Size Distributions using Machine Learning" (submitted/under revision). 
+
+The repository provides routines to perform particle size distribution (PSD) analysis, particularly workflows to estimate hydraulic conductivity with six Machine Learning (ML) algorithms:
 - Decision Tree (DT)
 - Random Forest (RF)
 - XGBoost (XG)