NY -- Standard & Poor's CreditWire 6/18/98 û Standard & Poor's today assigned its single-`A'-minus underlying rating (SPUR) to Montgomery County Higher Education & Health Authority, Pa.'s $46.5 million revenue bonds series 1998 dated June 1, 1998 due Dec. 31, 2021, issued for Pottstown Healthcare Corp. (PHC) The bonds, which are expected to receive a triple-`A' based on Financial Security Assurance Inc. bond insurance, are scheduled to sell June 25, 1998. At the same time, Standard & Poor's raised its rating on the authority's outstanding revenue bonds series 1991, also issued for Pottstown, to single-`A'-minus from triple-`B'-plus. The SPUR rating on the authority's series 1998 revenue bonds reflects: -- A solid business position in a service area with limited competition,