Every dense linear order complete set without endpoints having at most 
disjoint intervals is order isomorphic to the continuum
of real numbers, where 
is the set of natural numbers.
Souslin's Hypothesis
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References
Iyanaga, S. and Kawada, Y. (Eds.). "Souslin's Hypothesis." §35E.4 in Encyclopedic Dictionary of Mathematics. Cambridge, MA: MIT Press, p. 137, 1980.Referenced on Wolfram|Alpha
Souslin's HypothesisCite this as:
Weisstein, Eric W. "Souslin's Hypothesis." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/SouslinsHypothesis.html