  We describe a method to construct continuum spectra for radio sources on the
basis of entries from various source catalogues in comparatively large error
boxes around a given sky position. Sources from the UTR-2 catalogue (Braude et
al. 1978--1994), observed at decametric wavelengths (10--25 MHz) with an
antenna beam of about 40$'$, were cross-identified with entries from other
radio catalogues at higher frequencies. Using the CATS database we extracted
all sources within 40$'$ around UTR positions to find candidate
identifications. A spectrum for each source was fitted with a set of curves
using a least-squares method to find the best fit. We preferentially selected
radio counterparts whose radio spectrum extrapolated to low frequencies matched
the UTR decametric flux densities, and whose coordinates were close to the
gravity center of UTR positions. Among all the 1822 sources in the UTR
catalogue we found about 350 sources to be blends of two or more sources. As
the most probable true coordinates of the radio counterparts we used positions
from the NVSS, TXS, GB6, or PMN catalogues. Using low-frequency sources (26,
38, 85 MHz) from CATS we checked the reliability of some of our IDs. We show
examples of the above methods, including raw and ``cleaned'' spectra.
