Patterns of Deviation from the Standard Model
  Effective Lagrangians can be used to parametrize the effects of physics beyond the standard model. Assuming the complete theory is a gauge theory, we determine which effective operators may be generated at tree level, and which are only generated at loop level. The latter are be suppressed by factors of $1/ 16\pi^2$ and will therefore be quite difficult to detect. In particular, all operators changing the Standard-Model structure of the triple-gauge-vector couplings fall into this category. We also point out that in certain cases, dimension-eight operators may be more important than dimension-six operators. We discuss both the linear and non-linear representation of the Higgs sector. 
C. Arzt, M.B. Einhorn, and J. Wudka