A lot of books suggest baby being in bed by a set time - usually around 6 - 7 pm. (sleeptrainmybaby.com)
The point is that you likely won't be able to understand the point until you have a grasp of the topic at the level of basic concepts described in books I suggested. (judithcurry.com)
A new book suggests that smiling and other emotions like anger and resentment might not be universal expressions. (inc.com)