Added link to John Beale's C code for T6963. Added link to Toshiba's web page for T6963 PDF files. Added link to NEC graphic displays. The FTP intermittently refuses to work, please try later if it fails. The manufactures use the term Vcc-Vee to describe the LCD bias voltage.
Some displays have a negative LCD supply voltage AND a negative contrast control supply voltage.
An example of this is the DMF50081 from Optrex. Others have a single negative LCD supply voltage which also controls the contrast. From the Optrex DMF5005 data sheet. Most the manufactures seem to use some variation of this notation. Yes, I should have example schematics and real applications.