FTP, give this method named for three chemists whose surnames begin with the same letter.
This method uses zero-differential overlap approximations to account for electron-electron repulsions. It replaced the Huckel pi-electron theory in 1953 to describe molecular orbitals. FTP, give this method named for three chemists whose surnames begin with the same letter. 
This method uses zero-differential overlap approximations to account for electron-electron repulsions.
Pariser-Parr-Pople method (or PPP)