This is a fundamental and well-established principle of quantum mechanics regarding the angular dependence of atomic orbitals, requiring no citation.
The claim states that atomic orbitals are not spherically symmetric when the magnetic quantum number is non-zero (i.e., m is not equal to zero, such as in p_x, p_y, or d-orbitals which feature nodal planes or lobes breaking spherical symmetry). This is a foundational, axiomatic fact of quantum chemistry and atomic physics found in every introductory textbook, making it common knowledge by direct definition of spherical harmonics. None of the retrieved papers are targeted at verifying or contesting this textbook fact; they are specialized studies on unrelated topics such as fullerenes, topological semimetals, and high-harmonic generation.