...S&P Global Ratings assigned its '##-' long-term rating and stable outlook to Red Oak, Texas' series 2018 combination tax and revenue certificates of obligation and affirmed its '##-' long-term rating and underlying rating (SPUR), with a stable outlook, on the city's existing tax-backed general obligation (GO) debt. Revenue from a direct and continuing ad valorem tax levied, within the limits prescribed by law, on all taxable property in the city and a limited-surplus combined-utility-system-revenue pledge secure the certificates. However, we rate the certificates based on the city's ad valorem pledge. The city's GO bonds are payable from revenue of a direct and continuing ad valorem tax levied, within the limits prescribed by law, on all taxable property in the city. State statutes limit the maximum ad valorem tax rate to $2.50 per $100 of taxable assessed valuation. Administratively, Texas' attorney general permits the allocation of $1.50 for all GO debt based on the 90% tax-collection...