[en] The authors studied the low-temperature energy gap 2Δ_o on Bi₂Sr₂CaCu₂O₈+delta (Bi2212) and La_2-xSr_xCuO₄ (La214) systematically over a wide range of doping level p using STS, break junction tunneling spectroscopy, Raman scattering and low-T electronic specific heat data. They have also studied the electronic specific heat of La214 in the normal state at T > Tc, and confirmed that pseudogap behavior appears at around T*, below which the in-plane resistivity ρ and magnetic susceptibility χ tend to be slightly suppressed. Similar suppression appears in ρ and χ of Bi2212 below the onset temperature of pseudogap T*. It is pointed out in the present study that 2Δ_o is closely related to T* in both Bi2212 and La214 systems; T* approximately 2Δ_o/4.3 k_B. It is also pointed out that 2Δ_o is in almost linear proportion to k_BT_max(much_ltT*), where T_max is the temperature exhibiting a broad peak in χ-T curves and k_BT_max can be considered to give a measure of the effective antiferromagnetic exchange energy J_eff. The α factors in 2Δ_o approximately αk_BT_max approximately αJ_eff are approximately 1 for La214 and approximately 2 for Bi2212, respectively. They also report that in both Bi2212 and La214 systems Tc roughly scales with pΔ_o except in highly doped samples, where Tc ∝ 2Δ_o