This may sound like a rather stupid question, but what must be, must be.
I recently bought a Lonely Planet travel guide for Beijing (publ. 04-2013) and on the inside of the front cover, there are these symbols giving vital information for each listing. There's an icon for "WiFi", for "Family friendly", "Opening hours" etc. etc.
But not all icons/symbols used are listed here. For instance, they also use an icon that looks like a small quadrangle with a bold-faced "S" and it always comes with the name of a location(?). Also, there's this icon that looks like a small quadrangle containing what looks like a small "booklet" with the letter "E" on it.
What do these symbols mean and shouldn't have this guide a listing of ALL symbols used?