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: 0xE3 0x19 0xCA 0x55
2: PCDATA invalid Char value 25
3: Opening and ending tag mismatch: Grant line 2397 and MeshHeading
4: Opening and ending tag mismatch: GrantList line 2384 and MeshHeadingList
5: Opening and ending tag mismatch: Article line 2303 and MedlineCitation
6: Specification mandate value for attribute Pu
7: attributes construct error
8: Couldn't find end of Start Tag PubMedPubDate line 2432
9: Opening and ending tag mismatch: History line 2416 and MedlineCitation
10: Opening and ending tag mismatch: PubmedData line 2415 and PubmedArticle
11: expected '>'
12: Unescaped '<' not allowed in attributes values
13: attributes construct error
14: Couldn't find end of Start Tag DescriptorName line 3059
15: error parsing attribute name
16: attributes construct error
17: Couldn't find end of Start Tag PubMedPubDate line 3075
18: Opening and ending tag mismatch: History line 3074 and MeshHeading
19: Opening and ending tag mismatch: PubmedData line 3073 and MeshHeadingList
20: Opening and ending tag mismatch: PubmedArticle line 2888 and MedlineCitation
21: Opening and ending tag mismatch: MedlineCitation line 2291 and PubmedArticle
22: expected '>'
23: Premature end of data in tag PubmedArticleSet line 3

--- failed re-building ‘easyPM_vignette_html.Rmd’

--- re-building ‘easyPM_vignette_pdf.Rmd’ using rmarkdown
Warning in grep("\\\n$", msg) :
  input string 1 is invalid in this locale
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 0xE3 0x2B 0xB3
2: error parsing attribute name
3: attributes construct error
4: Couldn't find end of Start Tag Article<f0><e3> line 1963
5: Opening and ending tag mismatch: Reference line 1961 and ArticleIdList
6: Opening and ending tag mismatch: ReferenceList line 1918 and Reference
7: Opening and ending tag mismatch: PubmedData line 1871 and ReferenceList
8: Opening and ending tag mismatch: PubmedArticle line 1589 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_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