[EM] Sequential dropping towards a spanning tree - another immune method related to ranked pairs and river

[Markus Schulze]

Dear Jobst,

when the beatpath method is being used then the beatpaths
from the beatpath winner to the other candidates just form
an arborescence with the beatpath winner as the root. It
seems to me that "sequential dropping towards a spanning
tree" (SDST) just finds this arborescence so that SDST is
identical to the beatpath method.

Markus Schulze