Wikipedia
Perserikatan is a term commonly refers to national amateur football competitions in Indonesia held between 1931 and 1994 before the formation of Liga Indonesia, organized by the PSSI, the Indonesian football federation. The competition involved hundreds clubs in Indonesia and was divided into several levels.
In English, the term Perserikatan may literally translated to inter-association football championship as this competition involved all regional-level football associations in Indonesia.
Since 1970, in parallel, another national football league namely Galatama (The Premier League), was established for semi professional football clubs. Therefore, prior to 1994, when both Perserikatan and Galatama were merged into a new system called Liga Indonesia, both competitions existed in parallel.