title: How to concatenate word vectors to form sentence vector
body: <p>I have learned in some essays (Tomas Mikolov...) that a better way of forming the vector for a sentence is to concatenate the word-vector.</p>
  <p>but due to my clumsy in mathematics, I am still not sure about the details.</p>
  <p>for example,</p>
  <p>supposing that the dimension of word vector is m; and that a sentence has n words.</p>
  <p>what will be the correct result of concatenating operation?</p>
  <p>is it a row vector of 1 x m*n ?     or a matrix of m x n ?</p>