Two types of symmetry breaking effects in the chiral Lagrangians for heavy mesons are discussed: Heavy quark symmetry breaking due to finite heavy quark masses, and SU(3) symmetry breaking induced by the inequality of the light quark masses.
Chou, H. S., & Huang, K. N. (1994). Implications of Parity and Time‐Reversal Symmetries in Atoms. Chinese Journal of Physics, 32(2), 171-193. https://www.airitilibrary.com/Article/Detail?DocID=05779073-199404-201212210035-201212210035-171-193