Main class representatives for all homogeneous trades of size < 20 Listed in increasing order of size. ab ba ab`` ba`` ``cd ``dc abc` bca` cab` ```` abc``` da`b`` b`dc`` `cad`` `````` `````` abc``` dc`a`` b`dc`` `dab`` `````` `````` ab```` ba```` ``cd`` ``dc`` ````ef ````fe abc```` bd`a``` c`b`e`` `a`ed`` ``edc`` ``````` ``````` abcd```` badc```` cdab```` dcba```` ```````` ```````` ```````` ```````` abcd```` badc```` cdba```` dcab```` ```````` ```````` ```````` ```````` ab`````` ba`````` ``cd```` ``dc```` ````ef`` ````fe`` ``````gh ``````hg abc`````` bca`````` cab`````` ```def``` ```efd``` ```fde``` ````````` ````````` ````````` abc`````` bd`a````` c`b`e```` `a`f`d``` ``e`cf``` ```dfe``` ````````` ````````` ````````` abc`````` dc`a````` ``ecf```` ``af`e``` b```df``` `d``eb``` ````````` ````````` `````````