text: from urllib.parse import urlparse
  # the other main place to look for pdf links is links with PDF in the 'span' assocaited with the links ('a' tags)
  def explicit_pdf_links(soup, base_url):
      # we'll store all our pdf links in this list and return at the end
      pdf_link_list = []
       
      # looks for all the 'a' tags
      for link_tag in soup.find_all('a'):
          # When a PDF link is provided, there is almost always "PDF" in the span so lets start by looking at text assoc with the link.
          if ('pdf' or 'download this article') in link_tag.text.lower():
              # if found then get the url using the href value
              current_link = link_tag.get('href')
              # make sure its not none then complete for relative links
              if current_link:
                  # check to see if its a relative link
                  if current_link.startswith('/'):
                      if base_url is not None:
                          # we can build the link by parsing the request URL
                          parse_object = urlparse(base_url)
                          # we then build the full URL from all the parts (current link at the end)
                          current_link = f'{parse_object.scheme}://{parse_object.netloc}{current_link}'
                          pdf_link_list.append(current_link)
                      else:
                          # without a base to the URL the relative link is useless so we should ignore
                          pass
                  # if the link starts with http then its already a full link and we can save it
                  if current_link.startswith('http'):
                      pdf_link_list.append(current_link)
      # the previous approach should work for most htmls but i've come across  
      # some docs that embed the link within the span so we need to check the spans first
      if pdf_link_list == []:
          for link_tag in soup.find_all('span'):
              # The most common link has "Download PDF" in the span so lets start with that.
              if ('pdf' or 'download this article') in link_tag.text.lower():
                  # the href is the actual link attribute
                  a_tag = link_tag.find('a')
                  if a_tag:
                      current_link = a_tag.get('href')
                      if current_link:
                          # check to see if its a relative link
                          if current_link.startswith('/'):
                              if base_url is not None:
                                  # we can build the link by parsing the request URL
                                  parse_object = urlparse(base_url)
                                  # we then build the full URL from all the parts (current link at the end)
                                  current_link = f'{parse_object.scheme}://{parse_object.netloc}{current_link}'
                                  pdf_link_list.append(current_link)
                                                       
                          # if the link starts with http then its already a full link
                          if current_link.startswith('http'):
                              pdf_link_list.append(current_link)
  
              '''        for link_tag in soup.find_all('a',{'data-tooltip':'Download PDF'}):
              a_tag = link_tag.find('a')
              if a_tag:
                  current_link = a_tag.get('href')
                  if current_link:
                      # check to see if its a relative link
                      if current_link.startswith('/'):
                          if base_url is not None:
                              # we can build the link by parsing the request URL
                              parse_object = urlparse(base_url)
                              # we then build the full URL from all the parts (current link at the end)
                              if 'nejm' in parse_object.netloc:
                                  current_link = f'{parse_object.scheme}://{parse_object.netloc}{current_link}'
                                  pdf_link_list.append(current_link)'''
  
      return pdf_link_list