(2005) • Stumpf et al., Phys. Rev. E (2005) • Han et al., Nat. Biotech. (2005) • Lee et al., Phys. Rev. E (2006) • Costa et al., Phys. Rev. E (2007) random node/link sampling snowball sampling random link sampling (k=50 → 3) 0 500 1000 1500 2000 2500 0 2 4 6 8 10 12 14 P(k) k Random sampling does not explain why we have a decreasing P(k) so widely.