Related Clues:

• +, for short
• Opp. of 52 Across
• Minus: Abbr.
• No. beginning with a "-"
• Less than zero: Abbr.
• Pic source
• Battery abbr.
• Like nos. above zero
• Subzero (abbr.)
• Like nos. below zero
• Darkroom item, for short
• Blood-type abbr.
• Getters of letters: Abbr.
• Minus (Abbr.)
• +, on an AA batt.