A concept similar to that of PCR had been described before Mullis' work. Nobel laureate H. Gobind Khorana and Kjell Kleppe, a Norwegian scientist, authored a paper 17 years earlier describing a process they termed "repair replication" in the "Journal of Molecular Biology". Using repair replication, Kleppe duplicated and then quadrupled a small synthetic molecule with the help of two primers and DNA polymerase. The method developed by Mullis used repeated thermal cycling, which allowed the rapid and exponential amplification of large quantities of any desired DNA sequence from an extremely complex template. Later a heat-stable DNA polymerase was incorporated into the process.