Installing dimmer in four way switch circuit - DoItYourself.com Community Forums
ELEGRP Digital Dimmer Light Switch for 300W Dimmable LED/CFL Lights and 600W Incandescent/Halogen, Single Pole/3-Way LED Slide Dimmer Light Switch, Wall Plate Included, UL Listed, 1 Pack, Matte Black - Amazon.com
3-Way Dimmer Switch vs. Multi-Location Dimmer Switch — 1000Bulbs Blog
Lutron NT-4PS-TP Nova T 120V / 277V / 20A 4-Way Switch in Taupe, Matte Finish
Electrical dimmer switches for 4 switch locations? - Home Improvement Stack Exchange