I don't know about "writings", but unlike AdmiralBeatty (who's tickled OVER 300 WOMEN) I've only probably tickled like 70, but as someone who regularly has models clawing at the walls and begging for death (...that's a metaphor, no sue plz) I can say this;
Every person is different.
They have their own spots, their own preferences, their own mindsets, and their own responses to different techniques. It'll do you no good to go into every encounter thinking "If I just do XYZ she'll die laughing and love me forever", so that's why I spend the first five minutes or so of every shoot experimenting with the model and learning what works on her. Don't be afraid to ask for feedback on touch, pressure, sensitive spots, no-go zones (the most important one, IMHO), and - most imporantly - respect any and all stated boundaries, no questions asked. The only response you should ever give to "don't do X" is "ok".
And for the love of God, don't watch tickling videos for "research". Except mine, of course. Seriously though, it boggles my mind how much weird shit is passed off as "tickling" that wouldn't cause a single one of my girls to so much as crack a smile. I guess maybe there's something to the old saw about people faking it after all...
Anyway, tickling is a deeply personal thing whereby you forge a connection with the person you're doing it with; not just their body, but also their mind. It's about them, not you; keep that in mind and you'll always at least be starting on solid ground.
Good luck!
PS: OK, I lied. There is one thing you can definitely bank on; the notion that endlessly tickling someone non-stop in one spot (or even in general) is the way to go. People eventually get tired and shut down, so learn to keep an eye on your play partner and get a sense for when they need a break, or at least need you to switch spots. Again, ask for feedback. The quickest way to get someone to hate you and never play with you again is to ignore their wants and needs in favor of your own.