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: 0x8A 0x86 0x0C 0x7F
2: PCDATA invalid Char value 12
3: Specification mandate value for attribute Maj
4: attributes construct error
5: Couldn't find end of Start Tag DescriptorName line 2479
6: Unescaped '<' not allowed in attributes values
7: attributes construct error
8: Couldn't find end of Start Tag DescriptorName line 2497
9: expected '>'
10: Opening and ending tag mismatch: MeshHeadingList line 2471 and MedlineCitation
11: Opening and ending tag mismatch: MedlineCitation line 2290 and PubmedArticle
12: Specification mandate value for attribute IdType
13: attributes construct error
14: Couldn't find end of Start Tag ArticleId line 3136
15: Opening and ending tag mismatch: PubmedData line 3093 and Reference
16: Opening and ending tag mismatch: PubmedArticle line 2885 and ReferenceList
17: Opening and ending tag mismatch: PubmedArticle line 2289 and PubmedData
18: Opening and ending tag mismatch: PubmedArticleSet line 3 and PubmedArticle
19: 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 0x87 0x46
2: Opening and ending tag mismatch: Citation line 934 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: AuthorList line 1619 and Author
8: Opening and ending tag mismatch: Article line 1597 and AuthorList
9: Opening and ending tag mismatch: MedlineCitation line 1590 and Article
10: Opening and ending tag mismatch: PubmedArticle line 1589 and MedlineCitation
11: Opening and ending tag mismatch: AbstractText line 2302 and Abstract
12: Opening and ending tag mismatch: Abstract line 2301 and Article
13: Opening and ending tag mismatch: Article line 2281 and MedlineCitation
14: Opening and ending tag mismatch: MedlineCitation line 2269 and PubmedArticle
15: expected '>'
16: 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