)。 US Patent 1,647, Improvement in the mode of communicating information by signals by the application of electro-magnetism, June 20, 1840(页面存档备份,存于互联网档案馆)
Qingfeng; Liu, Shushuang. Evidence of ENSO signals in a stalagmite-based Asian monsoon record during the medieval warm period. Palaeogeography, Palaeoclimatology