checkEvents() method addresses S3 generic/method consistency

[auzaheta]

Description

• checkEvents() method addresses S3 generic/method consistency.
• Solve broken URL links in the bibliography.

Checklist:

• I have added tests that prove my fix is effective or that my feature works
• The package builds on my OS without issues (please add workstation details)
• My changes generate no new warnings
• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (.R, NEWS.md)
• I have bumped the version by the appropriate increment in the DESCRIPTION file (major, minor, patch)