They mention several times Queen Seon Duk and Bidam.
Also Bidam actions in Queen Seon Duk have consequences in Six Flying Dragons.

Other similarities:
- Same writers.
- Politics.
- The "bad" characters are also very charming.
- Strong female characters.
- Both dramas tell historical events.
- Almost there is no romance (Is more subtle compared to SFD).
- Action.

They have more things in common, like the treatment of the characters and the drama structure (the sequel A tree with deep roots also follow the same structure).