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   73016
   The combination of X-ray observations with ROSAT and the Green Bank
   radio survey has increased the number of BL Lacs ('RGB' BL Lacs), but
   has also blurred the classification. The RGB sample spans the region of
   log Sx/Sr occupied by radio selected BL Lacs (RBLs) and X-ray selected
   BL Lacs (XBLs) and also the region in between. We propose ASCA
   observations of three intermediate BL Lacs to (1) determine the main
   emission process responsible for their X-ray spectrum (synchrotron or
   synchrotron with a Compton component) (2) define their broad band
   (radio-X-ray) spectrum from which we can estimate the spectral break
   frequency and (3) compare ASCA results with XBLs and RBLs. Simultaneous
   radio and optical monitoring will be used to search for the
   microlensing achromatic signature.
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