I am not sure if Hankamer is right in claiming this property for it, but the allied concepts of unstressability and complete anaphoricity certainly are of use in distinguishing relative from interrogative pronouns, particularly undeclined relatives like pu which carry no information about the number, gender, or case of the NP they replace.

If Rodriguez slumps and the Yankees stumble, pressure will mount on a manager who failed to guide the team to the playoffs in 2008, the first time the Yankees missed the postseason in a nonstrike year since 1993.

an ancient name that is attested epigraphically

The Sanjiang Fold System is an Indosinian geosynclinal fold system, lying in western Yunnan and the Qamdo area of Tibet east of the Nujiang River and west of the Jinsha River. In eastern Tibet the Jinsha, Lancang and Nujiang Rivers turn suddenly to the south to form the famous Sanjiang (Three-River) Valley.