This article lays out the evidence for the Trinitarian God - i.e. 1 God made up of 3 persons: Father, Son and Holy Spirit. This is a foundational belief for Christianity.
http://www.bethinking.org/who-are-you-god/intermediate/the-historic-case-for-the-trinity.htm
Here is a quick reference to Biblical scriptures that point to a Trinitarian God:
http://billcluteairshows.com/Trinity.html
