This ODNI briefing from 15 May 2007 describes the rationale for ICREACH and the scale of metadata sharing that was envisioned: see the Intercept article The Surveillance Engine: How the NSA Built Its Own Secret Google, 25 August 2014.

This 21 September 2010 memo from the NSA’s CIA Liaison Support Group reveals that ICREACH is available to “over 1000 analysts across 23 US Intelligence Community agencies”: see the Intercept article The Surveillance Engine: How the NSA Built Its Own Secret Google, 25 August 2014.

This slide from an undated NSA presentation outlines the types of metadata the agency accesses and stores: see the book No Place To Hide, 13 May 2014.

This extract from a December 2010 NSA memo gives a broad overview of the NSA’s ICREACH middleware, including the participation of Second Party (Five Eyes) partner: see the Intercept article The Surveillance Engine: How the NSA Built Its Own Secret Google, 25 August 2014.

These extracts from the Congressional Budget Justification for the financial year 2013 show that increased funding was sought for ICREACH: see the Intercept article The Surveillance Engine: How the NSA Built Its Own Secret Google, 25 August 2014.

This memorandum dated 6 July 2005 describes features of the intelligence sharing systems that preceded ICREACH: see the Intercept article The Surveillance Engine: How the NSA Built Its Own Secret Google, 25 August 2014.

This 23 November 2004 decision memorandum from then-NSA Director Keith Alexander gives the initial go-ahead for the agency’s ICREACH system: see the Intercept article The Surveillance Engine: How the NSA Built Its Own Secret Google, 25 August 2014.