2.3 & 2.1 & -0.12\
& & -22.8 & A91 & 2.3 & &\
& & -23.5 & S93 & 1.6 & &\
& & -22.9 & this work & 2.2 & &\
PKS 2005–489 & -26.3 & -24.2 & S93 & 2.1 & 2.7 & -0.15\
& & -23.7 & F96 & 2.6 & &\
MS 2143.4$+$070 & -25.9 & -23.4 & W96 & 2.5 & 2.5 & -0.04\
PKS 2155–305 & -26.8 & -24.4 & F96 & 2.4$^a)$ & &\
PKS 2254$+$074 & -25.6: & -24.1 & S93 & 1.5: & 1.8: & 0.10:\
& & -23.9 & F96 & 1.7: & &\
& & -23.9 & W96 & 1.7: & &\
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[lllllll]{}\
\
& V–R & V–I & V–K & J–H & H–K & J–K\
\
Gregg (1989) & 0.58$\pm$0.11 & 1.23$\pm$0.22 & & & &\
Carollo (1997) & & 1.30$\pm$0.05 & & & &\
Schombert (1993) & & & 3.29$\pm$0.09 & & & 0.87$\pm$0.04\
Bressan, Chiosi & Tantalo (1996) & & & 3.28$\pm$0.11 & & &\
Recillas-Cruz (1990) & & & & 0.72$\pm$0.08 & 0.22$\pm$0.06 &\
Silva & Elston (1994) & & & & & & 0.90$\pm$0.02\
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