Ann: Investor Presentation, page-153

Certainly includes Production Taxes and Ad Valorem Taxes, which are both based on production rates / sales prices - but doesn't include corporate taxes.

Engineers aren't accountants and so they aren't qualified to calculate a corporate tax rate that takes into account all deductions going forward, including those that have nothing to do field-level level revenue i.e. head office costs.

I'll try and find a specific reference.