N.C. gratefully acknowledges financial support from a Marie Curie Intra-European grant (contract number MEIF-CT-2005-024660) and from FNRS (Belgium). P.H. was partially supported by the Polish MNiSW grant no. N20300632/0450.
We express our deep gratitude to D.G. Yakovlev for his help in the preparation of the present review. He read the whole manuscript and, during many hours of Skype sessions, he went over with one of us (P.H.) all the sections that required corrections, clarifications and improvement (they were legion). We thank him for his patience and expertise shared with us.
We are grateful to A.Y. Potekhin, who suggested several improvements in the sections referring to the effects of magnetic fields. He also suggested appropriate figures and made some new ones, which enriched the content of this review. Sometimes a good figure is better than hundreds of words.
We also thank Lars Samuelsson for his comments on elasticity and on axial modes in neutron stars.
We would like to address our gratitude to our colleagues, who contributed to this review through discussions or collaborations.
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