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 0x93 0x74 0x38
2: Opening and ending tag mismatch: Citation line 1072 and ArticleIdList
3: error parsing attribute name
4: attributes construct error
5: Couldn't find end of Start Tag Affiliati line 1718
6: Opening and ending tag mismatch: AffiliationInfo line 1735 and Author
7: expected '>'
8: Opening and ending tag mismatch: AuthorList line 1618 and Article
9: Opening and ending tag mismatch: Article line 1596 and MedlineCitation
10: Opening and ending tag mismatch: MedlineCitation line 1589 and PubmedArticle
11: expected '>'
12: 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 0x63 0x37 0xB8
2: Unescaped '<' not allowed in attributes values
3: attributes construct error
4: Couldn't find end of Start Tag ArticleId line 858
5: Opening and ending tag mismatch: ArticleIdList line 857 and Reference
6: expected '>'
7: Opening and ending tag mismatch: ReferenceList line 746 and PubmedData
8: Opening and ending tag mismatch: PubmedData line 704 and PubmedArticle
9: Opening and ending tag mismatch: JournalIssue line 1564 and MedlineCitation
10: Opening and ending tag mismatch: Journal line 1562 and PubmedArticle
11: Opening and ending tag mismatch: Article line 1561 and PubmedArticleSet
12: Premature end of data in tag Citation line 1554
13: Premature end of data in tag Reference line 1553
14: Premature end of data in tag ReferenceList line 1294
15: Premature end of data in tag PubmedData line 1253
16: Premature end of data in tag PubmedArticle line 1105
17: Premature end of data in tag PubmedArticle line 443
18: 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