Update README.md

README.md

@@ -15,7 +15,7 @@ elements in a sequence at a single nucleotide resolution. It is the result of fi
 but also the genomes of 5 selected species: mouse, chicken, fly, zebrafish and worm. 
 
 For the finetuning on the multi-species genomes, we curated a dataset of a subset of the annotations used to train **Segment-NT**, mainly because only this subset of annotations is
-available for these species. The annotations therefore concern the 7 main gene elements available from Ensembl [REF], namely protein-coding gene, 5’UTR, 3’UTR, intron, exon, 
+available for these species. The annotations therefore concern the 7 main gene elements available from [Ensembl](https://www.ensembl.org/index.html), namely protein-coding gene, 5’UTR, 3’UTR, intron, exon, 
 splice acceptor and donor sites.