  It has long been argued that the ground state of matter may be strange quark
matter (SQM), not hadronic matter. A whole sequence of SQM objects, ranging
from strange quark stars and strange quark dwarfs to strange quark planets, can
stably exist according to this SQM hypothesis. A strange dwarf has a mass
similar to that of a normal white dwarf but could harbor an extremely dense SQM
core (with a density as large as $\sim \rm 4\times10^{14}\,g\,cm^{-3} $) at the
center so that its radius can be correspondingly smaller. In this study, we try
to search for strange dwarfs among the observed "white dwarfs" by considering
their difference in the mass-radius relation. Eight strange dwarf candidates
are identified in this way, whose masses are in the range of $\sim 0.02
M_{\odot}$ -- $0.12 M_{\odot}$, with the radii narrowly distributed in $\sim$
9,000 km -- 15,000 km. The eight objects are SDSS J165143.45+364647.6, LSPM
J0815+1633, LP 240-30, BD+20 5125B, LP 462-12, WD J1257+5428, 2MASS
J13453297+4200437, and SDSS J085557.46+053524.5. Comparing with white dwarfs of
similar mass, these candidates are obviously smaller in radius. Further
observations with large radio/IR/optical telescopes on these interesting
candidates are solicited.
