Grobogan was exempt from the monopoly arrangements applying in the rest of directly-ruled Java because of a local industry producing salt from mud springs.
Brown, Colin, ‘Salt of the earth: farming the salt wells of Grobogan', Indonesia Circle 35 (1984), pp. 11-27.
Butcher, John, and Howard Dick, eds, The Rise and fall of revenue farming : business elites and the emergence of the modern state in Southeast Asia. New York: St. Martin's Press, 1993.
Knaap, Gerrit, et al., ‘A forgotten trade: salt in Southeast Asia 1670-1813', in Roderich Ptak and Dietmar Rothermund, eds, Emporia, commodities and entrepreneurs in Asian maritime trade, 15th to 18th centuries. Wiesbaden: Steiner, 1991, pp. 127-157.
Verslag betreffende de Opium- en Zoutregie en de Zoutwinning. Batavia: Landsdrukkerij, [various years].