HL-20 Personnel Launch System: differenze tra le versioni

*{{cita web|url=http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940030181_1994030181.pdf|titolo=Launch-Pad Abort Capabilities of the HL-20 Lifting Body|editore=NASA}}

*{{cita web|url=http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19910006695_1991006695.pdf|titolo=Design and Fabrication of the NASA HL-20 Full Scale Research Model|editore=NASA}}