Heres a the first paragraph...
At room temperature, 1,2-~cyclononadiene (1)['] will more
or less keep indefinitely. Its dimerisation takes place only at
about 130°C[2]. In this process, the racemic mixture affords
the 1,2-bis(methylene)cyclobutane derivatives cis-2, trans-2,
and 3 in the ratio of 5:10:1, whereas nonracemic 1 gives rise
predominantly to cis-2r3I
Where 1 is 1,2-cyclononadiene..