Add citation

README.md

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 This repository contains a collection of multi- and many-objective optimization problems
 with real-world applications for benchmarking multiobjective evolutionary algorithms (MOEAs).
+Please cite the following if using this code:
+
+> Zatarain Salazar, J., Hadka, D., Reed, P., Seada, H., & Deb, K. (2024). Diagnostic benchmarking of many-objective evolutionary algorithms for real-world problems. Engineering Optimization, 1–22. https://doi.org/10.1080/0305215X.2024.2381818
 
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