Activist Starboard Value has $1 billion Pfizer stake, taps former executives for help, sources say CNBCActivist investor Starboard Value takes $1 billion stake in Pfizer, WSJ reports Yahoo FinanceActivist Starboard takes $1B stake in Pfizer - WSJ Seeking AlphaActivist Firm Starboard Value Takes $1 Billion Stake in Pfizer to Spur Turnaroun Bloomberg