1. X. Gu, The cohomology of BPU(p^m) and polynomial invariants, Math. Z. 312, 36 (2026).

2. D. Crowley and X. Gu, On H^*(BPU_n;Z) and Weyl group invariants, Trans. Amer. Math. Soc. DOI: https://doi.org/10.1090/tran/9517, Published electronically: August 13, 2025.

3. X. Gu, Y. Zhang, Z. Zhang and L. Zhong, The p-primary subgroups of the cohomology of BPU_n in dimensions less than 2p + 5, Proc. Amer. Math. Soc., published electronically, May 27, 2022, DOI: 10.1090/proc/16000, arXiv: 2108.03571.

4. X. Gu, On the cohomology of the classifying spaces of projective unitary groups, J. Topol. Anal., Vol.13, No.02, pp.535-573 (2021). DOI:10.1142/S1793525320500211, arXiv: 1612.00506.

5. X. Gu, X. Wang, and J. Wu, The composition of R.Cohen's elements and the third periodic elements in stable homotopy groups of spheres, Osaka J. Math., 58(2): 367-382 (April 2021), arXiv:1903.02730.

6. X. Gu, Some torsion classes in the Chow ring and cohomology of BPGL_n, J. London. Math. Soc., 103.1(2021), 127-160. DOI:10.1112/jlms.12368, arXiv: 1901.10090.

7. X. Gu, The topological period-index problem over 8-complexes, II, Proc. Amer. Math. Soc. 148 (2020), 4531-4545. DOI:10.1090/proc/15112, arXiv: 1803.05100.

8. X. Gu, The topological period-index problem over 8-complexes, I, J. Topol., 12.4 (2019):1368-1395. DOI:doi.org/10.1112/topo.12119 arXiv: 1709.00787.