The high concentration (hcf.aov), high concentration log-likelihood ratio (hclr.aov),
log-likelihood ratio (lr.aov), embedding approach (embed.aov) or the non equal
concentration parameters approach (het.aov) is used.
References
Mardia K. V. and Jupp P. E. (2000). Directional statistics.
Chicester: John Wiley & Sons.
Rumcheva P. and Presnell B. (2017). An improved test of equality of mean
directions for the Langevin-von Mises-Fisher distribution.
Australian & New Zealand Journal of Statistics, 59(1): 119--135.
Tsagris M. and Alenazi A. (2024). An investigation of hypothesis testing procedures for circular
and spherical mean vectors. Communications in Statistics-Simulation and Computation, 53(3): 1387--1408.