发生在缩微文献上的油渍现象是胶片在长期的保存过程中较为普遍的衰变现象。
The grease phenomenon of microfilm documents is common decay phenomenon in the process of the long-term preservation.
根据不同的记录手段和读取方式，不健康文献可以分为∶印刷型、缩微型、机读型和视听型等。
According to different record means and reading ways, they can be divided into: printed, micro formed, read on machine and audio-visual etc.
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