In this paper a brief review is given of the basic theoretical concepts concerning the explanation of some of the recent experiments in superfluid 3He below 3 mK. In section 2 the experimental results for the phase diagram of the A- and B-phases, the shifts of the transverse and longitudinal resonance frequencies, and the specific heat jumps are discussed. Section 3 deals with the properties of the anisotropic BCS-states which are used to describe the A- and B-phases, i.e., the Anderson-Morel (AM) and the Balian-Werthamer (BW) state, respectively. In section 4 the origin of the strongly pressure dependent spin-fluctuations and their effect on the relative stability of the AM- and BW-states, the specific heat jumps, and the NMR-frequency-shifts is discussed. The main section 5 contains a description of the couplings between the fluctuations of the spin and the order parameter for triplet-pairing and the resulting effect, in particular, on the pressure dependence of the specific heat jump. Section 6 stresses the fundamental role the dipole interactions, together with the order parameter fluctuations, play in generating spin waves of a finite energy gap and thus longitudinal, NMR-resonance.
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