DisplayPort Standard
Mini DisplayPort Connector Standard
DisplayPort Interoperability Guideline (DP++)
DisplayPort Compliance Test Standards (CTS)
HDMI Specification

The HDMI Specification version 1.3a is available for free public download from the HDMI.org website here (via a bizarre "we will email you a one-time download link" system): https://www.hdmi.org/manufacturer/specification.aspx

For the sake of pure convenience, a directly-hosted copy of the specification (and older versions which were previously made available to the public, but are not archived on the HDMI website) can be accessed here: Please note that these versions have been made available to the public by HDMI Licensing and are archived here for historical and educational purposes only. These versions of the HDMI Specification are deprecated and should not be used for new designs. If you are a curious person and wish to know how the latest versions work inside, I highly encourage everyone to pay $5,000 a year to become a licensed HDMI Adopter.
HDMI Compliance Test Specification (CTS)
DVI Specification
Open LVDS Display Interface Specification
CTA Standards
ITU-R Broadcasting-Television Recommendations
DCI Digital Cinema System Specification
Other VESA Standards