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Freeman's law (i.e., the Freeman law) states that spiral galaxies have the same surface brightness at the center, i.e., within a small range, if any bulge is excluded. The law is not universally accepted: some surveys have supported it, but some observations have not and it has been argued that selection bias produced the apparent fact. A possibility is there exists a population that fits the law and another (e.g., low-surface-brightness galaxies) that does not.