The Prithvi reference article from the English Wikipedia on 24-Apr-2004
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Prithvi

In Hinduism, Prithvi (pṛthvī) is an Earth Mother, wife of Dyaus Pita, mother of Indra and Agni. Originally, they were both known as Dyavaprthivi. When Indra killed Dyaus Pita, she applauded and married him. She is associated with the cow.

Also spelt Prithivi, Prthivi.