Package check result: NOTE

Check: CRAN incoming feasibility, Result: NOTE
  Maintainer: ‘Jingmeng Cui <jingmeng.cui@outlook.com>’
  
  Found the following (possibly) invalid URLs:
    URL: https://www.doi.org/10.1063/1.4943096
      From: README.md
      Status: 403
      Message: Forbidden
    URL: https://www.doi.org/10.1073/pnas.0800579105
      From: README.md
      Status: 403
      Message: Forbidden

No changes to worse in reverse depends.