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 0xB3 0xB3 0x62
2: Opening and ending tag mismatch: Citation line 814 and Reference
3: expected '>'
4: Opening and ending tag mismatch: ReferenceList line 746 and PubmedData
5: Opening and ending tag mismatch: PubmedData line 704 and PubmedArticle
6: PCDATA invalid Char value 16
7: Opening and ending tag mismatch: Citation line 1525 and Reference
8: expected '>'
9: Opening and ending tag mismatch: ReferenceList line 1295 and PubmedData
10: Opening and ending tag mismatch: PubmedData line 1254 and PubmedArticle
11: error parsing attribute name
12: attributes construct error
13: Couldn't find end of Start Tag Med line 1560
14: Opening and ending tag mismatch: PubmedArticle line 1559 and Citation
15: Opening and ending tag mismatch: PubmedArticle line 1106 and Reference
16: Opening and ending tag mismatch: PubmedArticle line 443 and ReferenceList
17: Opening and ending tag mismatch: PubmedArticleSet line 3 and PubmedData
18: Extra content at the end of the document

--- 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 0x93 0x4A 0x23
2: Opening and ending tag mismatch: ReferenceList line 746 and Reference
3: Opening and ending tag mismatch: PubmedData line 704 and ReferenceList
4: Opening and ending tag mismatch: PubmedArticle line 443 and PubmedData
5: Opening and ending tag mismatch: PubmedArticleSet line 3 and PubmedArticle
6: 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