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 0xD3 0xF4 0x96
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: Opening and ending tag mismatch: ReferenceList line 1295 and Reference
7: Opening and ending tag mismatch: PubmedData line 1254 and ReferenceList
8: Opening and ending tag mismatch: PubmedArticle line 1106 and PubmedData
9: Opening and ending tag mismatch: PubDate line 4312 and JournalIssue
10: Opening and ending tag mismatch: JournalIssue line 4309 and Journal
11: Opening and ending tag mismatch: Journal line 4307 and Article
12: Opening and ending tag mismatch: Article line 4306 and MedlineCitation
13: Opening and ending tag mismatch: MedlineCitation line 4294 and PubmedArticle
14: Specification mandate value for attribute UcEbVASY06m
15: attributes construct error
16: Couldn't find end of Start Tag Re3 line 5758
17: PCDATA invalid Char value 16
18: error parsing attribute name
19: attributes construct error
20: Couldn't find end of Start Tag A line 5777
21: Opening and ending tag mismatch: ReferenceList line 5481 and Reference
22: Opening and ending tag mismatch: PubmedData line 5450 and ReferenceList
23: Opening and ending tag mismatch: PubmedArticle line 5257 and PubmedData

--- 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 0x48 0x32
2: Opening and ending tag mismatch: CopyrightInformation line 2914 and AbstractText
3: Opening and ending tag mismatch: JournalIssue line 2906 and Abstract
4: Opening and ending tag mismatch: Journal line 2904 and Article
5: Opening and ending tag mismatch: Article line 2903 and MedlineCitation
6: Opening and ending tag mismatch: MedlineCitation line 2891 and PubmedArticle
7: expected '>'
8: 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