plus, in remembrance: we look back at american poet john ashbery, his influential work and what made the prolific writer unique. >> poetry comes to me out of thin air or out of my unconscious mind. it's sort of the way dreams come to us. >> yang: all that and more on tonight's pbs newshour. >> major funding for the pbs newshour has been provided by: ♪ ♪ moving our economy for 160 years. bnsf, the engine that connects us. >> and the william and flora hewlett foundation, helping people build immeasurably better lives. >> and with the ongoing support of these institutions: and individuals. >> this program was made possible by the corporation for public broadcasting. and by contributions to your pbs station from viewers like you. thank you. >> yang: north korea has again seized the world's attention with a new nuclear blast. the weekend test may move pyongyang a quantum leap forward in its bid to become a nuclear power, capable of threatening the u.s. mainland. that, in turn, has set off a new diplomatic flurry. nick schifrin reports. >> enough is enough. >> reporter: for the second time

plus, in remembrance: we look back at american poet john ashbery, his influential work and what made the prolific writer unique.