Task: Question Answering
Input (English): The theorem is proven constructively by selecting the parameters of the multi-head self-attention layer so that the latter acts like a convolutional layer. 
 Question: How they prove that multi-head self-attention is at least as powerful as convolution layer? 
Output (English): constructively by selecting the parameters of the multi-head self-attention layer so that the latter acts like a convolutional layer