Fix Citation Information section in dataset cards (#4879)

Commit from https://github.com/huggingface/datasets/commit/60bdf3005d1dc0b26da8e5949721b20d932eaad6

README.md

@@ -150,7 +150,19 @@ This dataset is licensed under the Creative Commons Attribution-NonCommercial-Sh
 
 ### Citation Information
 
-[More Information Needed]
+Please consider citing the authors of the "One Million Post Corpus" if you use the dataset.:
+```
+@InProceedings{Schabus2017,
+  Author    = {Dietmar Schabus and Marcin Skowron and Martin Trapp},
+  Title     = {One Million Posts: A Data Set of German Online Discussions},
+  Booktitle = {Proceedings of the 40th International ACM SIGIR Conference on Research and Development in Information Retrieval (SIGIR)},
+  Pages     = {1241--1244},
+  Year      = {2017},
+  Address   = {Tokyo, Japan},
+  Doi       = {10.1145/3077136.3080711},
+  Month     = aug
+}
+```
 
 ### Contributions