Historical clue formulations

• "Shhhh!" prompter — 2008-09-01
• Admonition to a noisy child — 2003-02-07
• A proverb that contradicts 17- and 34-Across — 2001-09-17
• Librarian's motto, perhaps — 2001-03-19
• The squeaky wheel gets the grease, but also... — 1999-01-03
• Maxim violated by a stool pigeon — 1996-04-12