added Casey's & Tony's changes

[ci skip]

This build is based on
6be026c.

This commit was created by the following CI build and job:
https://github.com/greenelab/covid19-review/commit/6be026cad3004fba1e58294fce2e42baeca4ad14/checks
https://github.com/greenelab/covid19-review/runs/61492006

citations.tsv

@@ -6,4 +6,8 @@ isbn:9780262517638	isbn:9780262517638	isbn:9780262517638	zBPP9YKu
 pmcid:PMC6103790	pmcid:PMC6103790	pmcid:PMC6103790	PyydLU5l
 pmid:30718888	pmid:30718888	pmid:30718888	7XVI5bB4
 url:https://greenelab.github.io/meta-review	url:https://greenelab.github.io/meta-review	url:https://greenelab.github.io/meta-review	6acIRW4q
+url:https://www.who.int/docs/default-source/coronaviruse/situation-reports/20200121-sitrep-1-2019-ncov.pdf	url:https://www.who.int/docs/default-source/coronaviruse/situation-reports/20200121-sitrep-1-2019-ncov.pdf	url:https://www.who.int/docs/default-source/coronaviruse/situation-reports/20200121-sitrep-1-2019-ncov.pdf	Vb5KFWnO
+url:https://www.who.int/docs/default-source/coronaviruse/situation-reports/20200128-sitrep-8-ncov-cleared.pdf	url:https://www.who.int/docs/default-source/coronaviruse/situation-reports/20200128-sitrep-8-ncov-cleared.pdf	url:https://www.who.int/docs/default-source/coronaviruse/situation-reports/20200128-sitrep-8-ncov-cleared.pdf	fLTiwToY
+url:https://www.who.int/docs/default-source/coronaviruse/situation-reports/20200311-sitrep-51-covid-19.pdf	url:https://www.who.int/docs/default-source/coronaviruse/situation-reports/20200311-sitrep-51-covid-19.pdf	url:https://www.who.int/docs/default-source/coronaviruse/situation-reports/20200311-sitrep-51-covid-19.pdf	x9975iBK
+url:https://www.who.int/docs/default-source/coronaviruse/situation-reports/20200321-sitrep-61-covid-19.pdf	url:https://www.who.int/docs/default-source/coronaviruse/situation-reports/20200321-sitrep-61-covid-19.pdf	url:https://www.who.int/docs/default-source/coronaviruse/situation-reports/20200321-sitrep-61-covid-19.pdf	11JitNwZt
 wikidata:Q56458321	wikidata:Q56458321	wikidata:Q56458321	QhC8yJ7V