IRAS two-color diagram of observational results for the H₂O and SiO masers according to SRs, Miras, and OH/IR stars. The curved dashed line is the evolutionary track defined by W. van der Veen & H. Habing (1988). The blue dashed line indicates the two groups of post-AGB stars, LI (left of IRAS, blue group) and RI (Right of IRAS, red group; M. N. Sevenster 2002). Undetected sources are marked with the yellow inverted filled triangles, the green filled triangles represent sources with H₂O maser only detected sources, the blue triangles, circles, and squares indicate sources with SiO maser only detected sources, and the pink triangles, circles, and squares indicate sources with both H₂O and SiO maser detected sources. Triangles represent SRs, squares represent Miras, and circles represent OH/IR stars. The numbers indicate identification numbers in Table 1. The numbers indicated on the graph correspond to sources where SiO22 has been detected (#17, #21, #22, and #99), three famous sources for each type of SRs, Miras, and OH/IR stars (in total, nine stars) mentioned in Section 3 (#3, #13, #22, #50, #62, #83, #99, #106, and #117) and mentioned in Section 4.4 (#21, #26, #27, #46, #49, #79 and #99).