Beautiful pup in a gorgeous sweater!
I can't keep sweaters or coats on my hounds, but my old Shih Tzu and old Llasa Apso (both now deceased) loved their coats. I didn't knit them. I purchased them at PetsMart. A thick felted flannel fabric. The coats velcroed under their chin in the front, and under their belly. The coats kept them warm when we were in the mountains during hunting. It got awfully cold at night, and blustery in the daytime.
This is our (deceased) female hound and our (deceased) Llasa Apso, in the camper during hunting season. The hound has crammed herself into the Llasa's bed. Sigh. You can see the little flannel coat on the Llasa. It worked really well.
During cold spells these days, my husband has mellowed...and is totally in love with my current Shih Tzu. When it's cold up there in the mountains, I put her under the covers with me! Her crate (on the floor by my bed in the trailer) gets real cold. We keep the heat down low at night.