https://books.google.co.id/books?id=F7KlCgAAQBAJ&pg=PA83&lpg=PA83&dq=planet88&source=bl&ots=KBlouMqxGB&sig=ACfU3U16YhIy-cQWejzsdt4BWvIX2CMOhg&hl=id&sa=X&ved=2ahUKEwjxssG_45mFAxXGb2wGHcuuDT4Q6
https://books.google.co.id/books?id=F7KlCgAAQBAJ&pg=PA83&lpg=PA83&dq=planet88&source=bl&ots=KBlouMqxGB&sig=ACfU3U16YhIy-cQWejzsdt4BWvIX2CMOhg&hl=id&sa=X&ved=2ahUKEwjxssG_45mFAxXGb2wGHcuuDT4Q6