English: [From Vietnamese Wikipedia:] In 1995, Do Thi Phuong Bao improved the traditional zither to help it perform traditional pentatonic melodies, and at the same time, to perform 12-note melodies of Western music . Her improvement project has 4 main points: Expanding the table top to add strings to increase the range; Raising the height of the sound box made of sycamore wood to increase the efficiency of the resonance box, helping to increase the tone and volume; Continuous shaft legs; Adding a tuning set. Her improvement project of the zither was evaluated as excellent by the Scientific Council, and was also granted a Patent.