rework bibliography to show links

Author: Mischi

de/german-pension-poc/_bibliography.bib

@@ -1,24 +1,32 @@
-@online{safemath,
+@misc{safemath,
   title = {{OpenZeppelin Documentation - SafeMath}},
-  url = {https://docs.openzeppelin.com/contracts/2.x/api/math},
-  urldate = {2019-08-14}
+  howpublished = {\url{https://docs.openzeppelin.com/contracts/2.x/api/math}},
+  note = {Accessed: 2019-08-14}
 }
 
-@online{fixedpointnumbers,
+@misc{fixedpointnumbers,
   title = {{Solidity Documentation - Fixed Point Numbers}},
-  url = {https://solidity.readthedocs.io/en/v0.5.3/types.html#fixed-point-numbers},
-  urldate = {2019-08-14}
+  howpublished = {\url{https://solidity.readthedocs.io/en/v0.5.3/types.html#fixed-point-numbers}},
+  note = {Accessed: 2019-08-14}
 }
 
-@online{raf,
+@misc{raf,
   title = {{Rentenformel - Retenartfaktor}},
-  url = {https://de.wikipedia.org/wiki/Rentenformel#Rentenartfaktor_(RAF)},
-  urldate = {2019-08-14}
+  howpublished = {\url{https://de.wikipedia.org/wiki/Rentenformel#Rentenartfaktor_(RAF)}},
+  note = {Accessed: 2019-08-14}
 }
 
-@online{rente2018,
+@misc{rente2018,
   title = {{Versichertenbericht 2018}},
   author = {Deutscher Rentenversicherung Bund},
-  url = {https://www.deutsche-rentenversicherung.de/SharedDocs/Downloads/DE/Statistiken-und-Berichte/Berichte/versichertenbericht_2018.pdf?__blob=publicationFile&v=1},
-  urldate = {2019-08-14}
+  howpublished = {\url{https://www.deutsche-rentenversicherung.de/SharedDocs/Downloads/DE/Statistiken-und-Berichte/Berichte/versichertenbericht_2018.pdf?__blob=publicationFile&v=1}},
+  note = {Accessed: 2019-08-14}
 }
+
+
+@misc{rentezahlen2019,
+  title = {{Rentenversicherung in Zahlen 2019}},
+  author = {Deutscher Rentenversicherung Bund},
+  howpublished = {\url{https://www.deutsche-rentenversicherung.de/SharedDocs/Downloads/DE/Statistiken-und-Berichte/statistikpublikationen/rv_in_zahlen_2019.pdf?__blob=publicationFile&v=3}},
+  note = {Accessed: 2019-08-14}
+}