You can try Super Glue as described, I have done it successfully. Another thing I also have done is a little more extreme, namely cutting a couple of short transverse shallow grooves across the cracks on the back side, using a Dremel tool, then filling them with a good Epoxy. Or you could cut a long groove along the length of the crack. Clamp across the crack. Sand down the epoxy flush with the wood after it has cured.