Table 2

Candidate string for the example in Figure 1.

Candidate string

Population group

a

{O₁}, {O ₂, O₃}, {O₄}

b

{O₂, O₃}, {O₄}, {O₅}, {O₆}

c

{O₄}, {O₅}, {O₇}

Gu et al. International Journal of Health Geographics 2010 9:17   doi:10.1186/1476-072X-9-17