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: 0xD0 0xDD 0x9A 0xC3
2: Opening and ending tag mismatch: PubMedPubDate line 2560 and Reference
3: expected '>'
4: Opening and ending tag mismatch: Reference line 2586 and Refe
5: Opening and ending tag mismatch: History line 2537 and ReferenceList
6: Opening and ending tag mismatch: AbstractText line 2913 and Abstract
7: Opening and ending tag mismatch: Abstract line 2912 and Article
8: Opening and ending tag mismatch: Article line 2892 and MedlineCitation
9: expected '>'
10: expected '>'
11: Opening and ending tag mismatch: Reference line 3240 and Referen
12: Opening and ending tag mismatch: MedlineCitation line 2880 and PubmedArticle
13: PCDATA invalid Char value 3
14: Opening and ending tag mismatch: Citation line 4853 and ArticleIdList
15: PCDATA invalid Char value 16
16: Opening and ending tag mismatch: Citation line 6284 and Reference
17: expected '>'
18: Opening and ending tag mismatch: ReferenceList line 6054 and PubmedData
19: Opening and ending tag mismatch: PubmedData line 6023 and PubmedArticle
20: expected '>'
21: Premature end of data in tag PubmedArticle line 2879
22: 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 0x13 0x1E 0x13
2: PCDATA invalid Char value 19
3: PCDATA invalid Char value 30
4: PCDATA invalid Char value 19
5: Opening and ending tag mismatch: Citation line 814 and Reference
6: expected '>'
7: Opening and ending tag mismatch: ReferenceList line 740 and PubmedData
8: Opening and ending tag mismatch: PubmedData line 698 and PubmedArticle
9: Couldn't find end of Start Tag Citation line 1525
10: PCDATA invalid Char value 16
11: Specification mandate value for attribute PubMode70-6
12: attributes construct error
13: Couldn't find end of Start Tag Article line 1561
14: Opening and ending tag mismatch: MedlineCitation line 1554 and Citation
15: Opening and ending tag mismatch: PubmedArticle line 1553 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_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