Package check result: NOTE

Check: CRAN incoming feasibility, Result: NOTE
  Maintainer: ‘Alexander Ilich <ailich@usf.edu>’
  
  Found the following (possibly) invalid URLs:
    URL: https://prism.ucalgary.ca/bitstream/handle/1880/51900/texture%20tutorial%20v%203_0%20180206.pdf
      From: DESCRIPTION
            inst/doc/README.html
            README.md
      Status: Error
      Message: SSL peer certificate or SSH remote key was not OK [prism.ucalgary.ca]: server verification failed: certificate signer not trusted. (CAfile: /etc/ssl/certs/ca-certificates.crt CRLfile: none)

No changes to worse in reverse depends.