No, sorry. Reading any single one of those notes will unlock the non-lethal option. Reading any of the other notes afterwards will have no effect. The protagonist only has to read one note to get the option, but it can be any of those five.
It's possible that there are other things that could unlock it too (I'm thinking Persuading Sokolov and Winning Anton over), but even if they do, it would still be only one that is required to get the non-lethal option.
However, I don't think we need to link each note that activates the opportunity in the trivia of every other note just yet, as there may be too many to add and the corresponding trivia points becoming cumbersome on each page.