I have worked with four categories of organizations - enterprises, service providers, investment firms and industry bodies - in my career and many of the executives for whom I have been trusted advisor are personal references.
Some of my personal references are following...
CEOs and vertical business heads of pure play engineering service providers
Engineering business heads and vertical business heads of leading IT service providers
Strategy and marketing heads of leading engineering and IT service providers
Co-founder of a $1.3 billion PE fund
Engineering vendor management lead of one of the top five firm globally by market capitalization
Indian GIC head of a leading media technology enterprise
Global engineering head of one of the biggest conglomerates