diff --git a/README.md b/README.md
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@@ -60,4 +60,4 @@ The newly developed software is licensed under GNU General Public License v3.0.
 - Raju, D.N., Hansen, J.N., Rassmann, S., et al. **2019**. Cyclic Nucleotide-Specific Optogenetics Highlights Compartmentalization of the Sperm Flagellum into cAMP Microdomains. *Cells*. 8, 648. https://doi.org/10.3390/cells8070648. (https://www.mdpi.com/2073-4409/8/7/648)
 - Striggow, F., Medina‐Sánchez, M., et al. **2020**. Sperm‐Driven Micromotors Moving in Oviduct Fluid and Viscoelastic Media. *Small*. 16, 2000213. https://doi.org/10.1002/smll.202000213. (https://onlinelibrary.wiley.com/doi/full/10.1002/smll.202000213)
 - Oura, S., Kazi, S., et al. **2020**. *Cfap97d1* is important for flagellar axoneme maintenance and male mouse fertility. *PLOS Genetics*. 16(8): e1008954. https://doi.org/10.1371/journal.pgen.1008954. (https://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1008954)
-- Balbach, M., Hamzeh, H., et al. **2020**. Molecular Mechanism Underlying the Action of Zona-pellucida Glycoproteins on Mouse Sperm. *Frontiers in Cell and Developmental Biology*. 8:572735. Doi: https://doi.org/10.3389/fcell.2020.572735. (https://www.frontiersin.org/articles/10.3389/fcell.2020.572735/full)
+- Balbach, M., Hamzeh, H., et al. **2020**. Molecular Mechanism Underlying the Action of Zona-pellucida Glycoproteins on Mouse Sperm. *Frontiers in Cell and Developmental Biology*. 8:572735. https://doi.org/10.3389/fcell.2020.572735. (https://www.frontiersin.org/articles/10.3389/fcell.2020.572735/full)