1) Postscript image data 
Panel Study of Income Dynamics. Data set often used in labor economics studies. Data is from U.S. and is put together at the University of Michigan. Since 1968 the PSID has followed and interviewed annually a national sample that began with about 5000 families. Low-income families were over-sampled in the original design. Interviews are usually con...
PostScript Image Data
Pounds per square inch differential. Pressure difference between two points. 
pounds per square inch, differential.