Update README.md

Author: lemire

README.md

@@ -6,7 +6,9 @@ This is a research library currently. It is not meant for production use.
 
 Developers might want to consider our [Header-only Xor Filter library in C](https://github.com/FastFilter/xor_singleheader/).
 
-Reference: [Xor Filters: Faster and Smaller Than Bloom and Cuckoo Filters](https://arxiv.org/abs/1912.08258), Journal of Experimental Algorithmics (to appear).
+## Reference
+
+* Thomas Mueller Graf,  Daniel Lemire, [Xor Filters: Faster and Smaller Than Bloom and Cuckoo Filters](https://arxiv.org/abs/1912.08258), Journal of Experimental Algorithmics 25 (1), 2020. DOI: 10.1145/3376122