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: 0xCF 0x22 0x02 0x3D
2: PCDATA invalid Char value 2
3: Opening and ending tag mismatch: Reference line 2099 and Author
4: Opening and ending tag mismatch: Author line 2117 and ArticleIdList
5: Opening and ending tag mismatch: ReferenceList line 1918 and Reference
6: Opening and ending tag mismatch: PubmedData line 1871 and ReferenceList
7: Opening and ending tag mismatch: PubmedArticle line 1589 and PubmedData
8: Opening and ending tag mismatch: PubmedArticleSet line 3 and PubmedArticle
9: 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: 0x80 0x64 0x1C 0xC7
2: PCDATA invalid Char value 28
3: Opening and ending tag mismatch: JournalIssue line 2906 and AffiliationInfo
4: Opening and ending tag mismatch: Journal line 2904 and Author
5: Opening and ending tag mismatch: Article line 2903 and AuthorList
6: Opening and ending tag mismatch: MedlineCitation line 2891 and Article
7: Specification mandate value for attribute and
8: attributes construct error
9: Couldn't find end of Start Tag DDB2 line 2933
10: Opening and ending tag mismatch: ChemicalList line 2928 and AbstractText
11: Opening and ending tag mismatch: PubmedArticle line 2890 and Abstract
12: Opening and ending tag mismatch: PubmedArticleSet line 3 and Article
13: 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