The stupendous power of the Tevatron made possible the 1995 discovery of the top quark - the last of six flavors of quarks predicted by the standard model theory of particle physics.
6 types of quark were discovered before the top quark.
The top quark was the last of the 6 types, so only 5 types could have been discovered before it.
( z1 discover :ARG1 ( z2 quark :mod ( z3 type :quant 6 ) ) :time ( z4 before :op ( z5 quark :mod ( z6 top ) ) ) )