4U 1957+11: a persistent low-mass X-ray binary and black-hole candidate in the high state?
4U 2129+12
4U 2129+47
4U 2129+47 = V1727 Cygni
4U 2129+47: A Powerful Probe of Quiescent Neutron Star Emission
4U 2206+54
4U0115+63 Hard X-ray Images and Spectra from the InFOCuS Experiment
4U0241+61 - A luminous low-redshift QSO
4U1722 + 11 - The discovery of an X-ray selected BL Lac object
4U1755-33 in Quiescence
4U2206+54 - an Unusual High Mass X-ray Binary with a 9.6 Day Orbital Period but No Strong Pulsations
4U:0115+63
4U:2129+47 / V1727-CYGNI - a Low-Mass X-Ray Binary in an Extended Quiescent State
4vesta
4x288 linear array with hybrid ROIC (CCD + CMOS)
4x32 FIRGA array: a pacesetter for a 52x32-element gallium arsenide focal plane array
4μ - 8μ Spectrophotometric Observations from the NASA Flying 36" Telescope.
4ω Thomson scattering probe for high-density plasma characterization at Titan