Error(s) in re-building vignettes:
  ...
duplicated vignette title:
  ‘Retrieving and Analyzing PubMed Records via easyPubMed’

--- re-building ‘easyPM_vignette_html.Rmd’ using rmarkdown
Quitting from lines 39-50 (easyPM_vignette_html.Rmd) 
Error: processing vignette 'easyPM_vignette_html.Rmd' failed with diagnostics:
1: Input is not proper UTF-8, indicate encoding !
Bytes: 0xF0 0x13 0xC9 0x4B
2: invalid character in attribute value
3: attributes construct error
4: Couldn't find end of Start Tag ArticleId line 858
5: PCDATA invalid Char value 19
6: Opening and ending tag mismatch: ArticleIdList line 857 and Reference
7: expected '>'
8: Opening and ending tag mismatch: ReferenceList line 746 and PubmedData
9: Opening and ending tag mismatch: PubmedData line 704 and PubmedArticle
10: Opening and ending tag mismatch: JournalIssue line 1564 and MedlineCitation
11: Opening and ending tag mismatch: Journal line 1562 and PubmedArticle
12: Opening and ending tag mismatch: PubmedData line 4387 and MeshHeading
13: Opening and ending tag mismatch: MeshHetText line 5265 and AbstractText
14: Opening and ending tag mismatch: PubmedArticle line 4283 and Abstract
15: Opening and ending tag mismatch: Citation line 1554 and MedlineCitation
16: Opening and ending tag mismatch: ArticleIdList line 5591 and ReferenceList
17: Opening and ending tag mismatch: Reference line 5589 and PubmedData
18: Opening and ending tag mismatch: ReferenceList line 5456 and PubmedArticle
19: PCDATA invalid Char value 16
20: Opening and ending tag mismatch: Chemical line 6628 and MeshHeading
21: Opening and ending tag mismatch: ChemicalList line 6587 and MeshHeadingList
22: Opening and ending tag mismatch: PubmedData line 5425 and PubmedArticleSet
23: Premature end of data in tag Reference line 1553
24: Premature end of data in tag ReferenceList line 1294
25: Premature end of data in tag PubmedData line 1253
26: Premature end of data in tag PubmedArticle line 1105
27: Premature end of data in tag PubmedArticle line 443
28: Premature end of data in tag PubmedArticleSet line 3

--- failed re-building ‘easyPM_vignette_html.Rmd’

--- re-building ‘easyPM_vignette_pdf.Rmd’ using rmarkdown
Quitting from lines 39-50 (easyPM_vignette_pdf.Rmd) 
Error: processing vignette 'easyPM_vignette_pdf.Rmd' failed with diagnostics:
1: Input is not proper UTF-8, indicate encoding !
Bytes: 0xF0 0xC3 0x3A 0xF2
2: Opening and ending tag mismatch: Reference line 2009 and ArticleIdList
3: Opening and ending tag mismatch: ReferenceList line 1918 and Reference
4: Opening and ending tag mismatch: PubmedData line 1871 and ReferenceList
5: Opening and ending tag mismatch: PubmedArticle line 1589 and PubmedData
6: Opening and ending tag mismatch: PubmedArticleSet line 3 and PubmedArticle
7: Extra content at the end of the document

--- failed re-building ‘easyPM_vignette_pdf.Rmd’

SUMMARY: processing the following files failed:
  ‘easyPM_vignette_html.Rmd’ ‘easyPM_vignette_pdf.Rmd’

Error: Vignette re-building failed.
Error: Duplicate vignette titles.
  Ensure that the %\VignetteIndexEntry lines in the vignette sources
  correspond to the vignette titles.
Execution halted