Operads of finite posets
  We describe four natural operad structures on the vector space generated by isomorphism classes of finite posets. The three last ones are set-theoretical and can be seen as a simplified version of the first, the same way the NAP operad behaves with respect to the pre-Lie operad. Moreover the two first ones are isomorphic. 
Fr\'ed\'eric Fauvet, Lo\"ic Foissy, Dominique Manchon
math.CO