iOS 8 on the iPhone 4S: Performance isn't the (only) problem

New OS wants screen space and processing power that the old phone doesn't have.

Apple fixes iPhone battery issues

iPhone 4S review - The Verge

Apple iPhone 4S Review

iPhone 4S owners file suit against Apple, claim iOS 9 made phones unbearably slow : r/technology

iOS 9 on the iPhone 4S: A stay of execution, nothing more

Apple hit with class action lawsuit over iOS 9's performance on older iPhones - 9to5Mac

iOS 8 on the iPhone 4S: Performance isn't the (only) problem

iOS 8 on the iPhone 4S: Performance isn't the (only) problem

Will Apple stop supporting iOS on iPhones older than five years old? - Quora

We Double Dog Dare You To Read AnandTech's Entire iPhone 4S Review

iPhone 4S Review

iPhone 4S: First Impressions - by Christian Boyce