 We then propose two diffusion-based methods, BirgRank and AptRank, both of which use PageRank to diffuse information flows on this two-layer  model.
<clarity>  We then propose two diffusion-based methods, BirgRank and AptRank, both of which use PageRank to diffuse information flows on this two-layer  model.
 We then propose two diffusion-based methods, BirgRank and AptRank, both of which use PageRank to diffuse information on this two-layer model.