Brain teaser to challenge your frontal lobes - SharpBrains
58 Brain Teasers with Answers: Brain Teasers That Will Stump You
Amazon.com: 60-Second Brain Teasers Pencil-Free Puzzles: Short Head-Scratchers from the Easy to Near Impossible: 9781592339778: Haselbauer, Nathan: Books
58 Brain Teasers with Answers: Brain Teasers That Will Stump You