Running examples in 'biblio-Ex.R' failed
The error most likely occurred in:

> ### Name: doi2bib
> ### Title: Downloading bibliogrphic references from DOIs
> ### Aliases: doi2bib
> 
> ### ** Examples
> 
> ## Retrieve bibliographic entries for two publications
> dois <- c("10.1111/1748-5967.12330",
+     "10.1016/j.envsci.2019.03.017")
> 
> bibrefs <- doi2bib(dois)
Warning: 10.1111/1748-5967.12330 agency not found - proceeding with 'crossref' ...
Warning: 10.1111/1748-5967.12330 w/ (500) - <!DOCTYPE html>
<html lang="en-us">
<head>

    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <title>Error: DOI Cannot Connect to Server</title>



    <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.0.2/dist/css/bootstrap.min.css"
          rel="stylesheet"
          integrity="sha384-EVSTQN3/azprG1Anm3QDgpJLIm9Nao0Yz1ztcQTwFspd3yD65VohhpuuCOmLASjC"
          crossorigin="anonymous">
    <script
            src="https://cdn.jsdelivr.net/npm/bootstrap@5.0.2/dist/js/bootstrap.bundle.min.js"
            integrity="sha384-MrcW6ZMFYlzcLA8Nl+NtUVF0sA7MsXsP1UyJoMp4YLEuNSfAP+JcXn/tWtIaxVXM"
            crossorigin="anonymous">
    </script>

    <script src="https://kit.fontawesome.com/731b8140c4.js" crossorigin="anonymous"></script>

    <link rel="stylesheet" href="/static/css/style.css" integrity="">

    <style>
        @import url("https: [... truncated]
Warning: 10.1016/j.envsci.2019.03.017 agency not found - proceeding with 'crossref' ...
Warning: 10.1016/j.envsci.2019.03.017 w/ (500) - <!DOCTYPE html>
<html lang="en-us">
<head>

    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <title>Error: DOI Cannot Connect to Server</title>



    <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.0.2/dist/css/bootstrap.min.css"
          rel="stylesheet"
          integrity="sha384-EVSTQN3/azprG1Anm3QDgpJLIm9Nao0Yz1ztcQTwFspd3yD65VohhpuuCOmLASjC"
          crossorigin="anonymous">
    <script
            src="https://cdn.jsdelivr.net/npm/bootstrap@5.0.2/dist/js/bootstrap.bundle.min.js"
            integrity="sha384-MrcW6ZMFYlzcLA8Nl+NtUVF0sA7MsXsP1UyJoMp4YLEuNSfAP+JcXn/tWtIaxVXM"
            crossorigin="anonymous">
    </script>

    <script src="https://kit.fontawesome.com/731b8140c4.js" crossorigin="anonymous"></script>

    <link rel="stylesheet" href="/static/css/style.css" integrity="">

    <style>
        @import url("h [... truncated]
Error in x$content : $ operator is invalid for atomic vectors
Calls: doi2bib -> read_bib -> sub -> is.factor
Execution halted