"1997–98 El Niño"(PDF). National Aeronautics and Space Administration. 1999. Archived from the original(PDF) on 18 February 2013. Retrieved 12 February 2011.
El Niño and climate forecasting (Report). National Institute of Water and Atmospheric Research. Archived from the original on 23 April 2015. Retrieved 28 July 2015.
"1997–98 El Niño"(PDF). National Aeronautics and Space Administration. 1999. Archived from the original(PDF) on 18 February 2013. Retrieved 12 February 2011.
El Niño and climate forecasting (Report). National Institute of Water and Atmospheric Research. Archived from the original on 23 April 2015. Retrieved 28 July 2015.