Vlad the Impaler = Dracula--- How was this determined?

Question:

Vlad the Impaler = Dracula--- How was this determined?

If Bram Stoker used Vlad the Impaler as his "model" for Dracula, how was this fact determined? Did Stoker ever mention or refer to The Impaler?

Did James Joyce "miss" Inbad, the Impaler" ?

Best Answer - Chosen by Asker: Because he studied Vlad Tepech.