I don't remember the article but I have several unheated moveable, greenhouses that have been growing salad greens all winter here in zone 5/6. I also use a lot of row covers all winter for things a bit hardier than lettuce like garlic and spinach
What do you want to know?
There is also a couple of great books by Eliot Coleman about winter gardening without heat. He does this in Maine very successfully. one is called the "Winter Harvest Handbook: Gardening on the Backside of the Calander"
I beleieve that hoophouse gardening is the wave of the future