New fermions and a vector-like third generation in $SU(3)_c\otimes   SU(3)_L\otimes U(1)_N$ models
  We study two 3-3-1 models with i) five (four) charge 2/3 ($-1/3$) quarks and, ii) four (five) charge 2/3 ($-1/3$) quarks and a vector-like third generation. Possibilities beyond these models are also briefly considered. 
V. Pleitez