His groups

- Philosophy
- 7,128 members

- The Reading Room
- 5,643 members

- Gamers
- 9,445 members

- Positive Menta...
- 1,131 members

- Free Thinkers
- 2,566 members

- Science Junkie
- 10,597 members

- Personal Devel...
- 3,553 members

- Beatles
- 593 members

- Evolution
- 1,097 members

- Personality
- 5,707 members

- And Not a Book...
- 679 members

- Movies
- 4,629 members

- Futurism
- 2,853 members

- Star Trek
- 264 members

- Comic Books
- 255 members

- Physics
- 1,746 members

- Sci Fi Movies
- 1,134 members

- Skepticism and...
- 271 members

- Synchronicity
- 3,865 members

- Turn Off Your ...
- 1,514 members

- Mathematics
- 1,137 members

- Podcast Junkie
- 22 members

- History
- 684 members

- Engineering
- 614 members

- BBC
- 86 members

- Bookcrossing
- 105 members

- Coffee
- 1,066 members

- Extreme Tech
- 1,017 members

- Podcasting
- 162 members

- Teachers
- 35 members

- Archaeology
- 70 members

- Lifehackers
- 270 members

- Classic Rock &...
- 440 members

- Quotations & P...
- 1,004 members

- Memetics
- 557 members

- Retro
- 316 members

- Sci-Fi & Horro...
- 196 members

- Emergent Systems
- 441 members

- Wikipedia
- 838 members

- Mind
- 276 members

- Anthropology
- 300 members

- Star Fleet
- 42 members

- Steampunk
- 88 members

- LibraryThing
- 28 members
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