Spectra of the 16 maser sources listed in Table 1. Each spectrum is an amplitude scalar average of one-second integrations of all data on all baselines. (a) 6.7 GHz methanol maser − G023.25−00.24 (third epoch). (b) 6.7 GHz methanol maser − G028.14−00.00 (first epoch). (c) 22 GHz water maser − G028.86+00.06 (second epoch). (d) 6.7 GHz methanol maser − G029.86−00.04 (second epoch). (e) 6.7 GHz methanol maser − G029.95−00.01 (second epoch). (f) 22 GHz water maser − G029.98+00.10 (second epoch). (g) 6.7 GHz methanol maser − G030.22−00.18 (second epoch). (h) 6.7 GHz methanol maser − G030.41−00.23 (first epoch). (i) 6.7 GHz methanol maser − G030.70−00.06 (second epoch). (j) 6.7 GHz methanol maser − G030.74−00.04 (second epoch). (k) 6.7 GHz methanol maser − G030.78+00.20 (second epoch). (l) 6.7 GHz methanol maser − G030.81−00.05 (second epoch). (m) 6.7 GHz methanol maser − G030.97−00.14 (second epoch). (n) 22 GHz water maser − G031.41+00.30 (second epoch). (o) 6.7 GHz methanol maser − G032.04+00.05 (second epoch). (p) 6.7 GHz methanol maser − G033.09−00.07 (second epoch).