code: func (api *API) SubmitWork(nonce types.BlockNonce, hash, digest common.Hash) bool {
  	if api.ethash.config.PowMode != ModeNormal && api.ethash.config.PowMode != ModeTest {
  		return false
  	}
  
  	var errc = make(chan error, 1)
  
  	select {
  	case api.ethash.submitWorkCh <- &mineResult{
  		nonce:     nonce,
  		mixDigest: digest,
  		hash:      hash,
  		errc:      errc,
  	}:
  	case <-api.ethash.exitCh:
  		return false
  	}
  
  	err := <-errc
  	return err == nil
  }
docs: // SubmitWork can be used by external miner to submit their POW solution.
  // It returns an indication if the work was accepted.
  // Note either an invalid solution, a stale work a non-existent work will return false.