K. B. Dinh, K. A. Tran, T. H. Chau, V. K. Truong, H. B. Nguyen, H. T. Nguyen, T. P. Ho and L. V. Dao, Generation and application of four-wave mixing in collinear high harmonic generation, Comm. Phys. 33 (2023) 123. DOI: https://doi.org/10.15625/0868-3166/17928.