?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.aufirst=Rudi&rft.au=Haryadi%2C+Rudi&rft.aulast=Haryadi&rft.title=JPPPF&rft.atitle=Discovery+Learning+based+on+Natural+Phenomena+to+Improve+Students'+Science+Process+Skills&rft.genre=article