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 0x03 0x41 0x91
2: PCDATA invalid Char value 3
3: PCDATA invalid Char value 26
4: Opening and ending tag mismatch: ReferenceList line 2583 and Reference
5: expected '>'
6: Opening and ending tag mismatch: Reference line 2626 and Referen
7: Opening and ending tag mismatch: PubmedData line 2536 and ReferenceList
8: Opening and ending tag mismatch: PubmedArticle line 2284 and PubmedData
9: Opening and ending tag mismatch: PubmedArticleSet line 3 and PubmedArticle
10: 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: 0xC0 0x96 0x19 0xE7
2: PCDATA invalid Char value 25
3: PCDATA invalid Char value 22
4: Opening and ending tag mismatch: ArticleId line 2683 and ReferenceList
5: Opening and ending tag mismatch: ArticleIdList line 2682 and PubmedData
6: Opening and ending tag mismatch: Reference line 2680 and PubmedArticle
7: Opening and ending tag mismatch: Article line 2708 and Reference
8: Opening and ending tag mismatch: MedlineCitation line 2696 and ReferenceList
9: Opening and ending tag mismatch: PubmedArticle line 2695 and PubmedData
10: Opening and ending tag mismatch: ReferenceList line 2583 and PubmedArticle
11: AttValue: " or ' expected
12: attributes construct error
13: Couldn't find end of Start Tag ArticleDate line 3003
14: expected '>'
15: Opening and ending tag mismatch: MedlineCitation line 2890 and Article
16: Opening and ending tag mismatch: PubmedArticle line 2889 and MedlineCitation
17: StartTag: invalid element name
18: expected '>'
19: Opening and ending tag mismatch: ReferenceList line 3142 and PubmedData
20: Opening and ending tag mismatch: PubmedData line 3096 and PubmedArticle
21: Opening and ending tag mismatch: Journal line 3384 and ReferenceList
22: Opening and ending tag mismatch: Article line 3383 and PubmedData
23: Opening and ending tag mismatch: MedlineCitation line 3371 and PubmedArticle
24: expected '>'
25: Premature end of data in tag PubmedData line 2536
26: Premature end of data in tag PubmedArticle line 2284
27: Premature end of data in tag PubmedArticleSet line 3

--- 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