Should I add "and" in the sentence "We provide services for both..."? Which sentence is better in formal writing? "We provide services for both international companies from China, India, USA, Canada and domestic firms." "We provide services for both international companies from China, India, USA, Canada, and domestic firms." "We provide services for both international companies from China, India, USA and Canada and domestic firms." "We provide services for both international companies from China, India, USA and Canada, and domestic firms." The main questions are whether "and" should be inserted before "Canada", and whether "," should be inserted before "domestic", to make the sentence clear and formal. Feel free to rewrite them if you feel there is a better option. Also, when reading the sentence, would you understand "domestic firms" as firms from the same place as the service provider? If not, what would you suggest to revise it? Thank you very much!