Reference
Seventh Chords in Minor Scales
Since there are three types of minor scales (natural, harmonic, and melodic), there is a greater variety of seventh chords in these scales.
Seventh Chords in the Natural Minor Scale
Seventh Chords in the Harmonic Minor Scale
Seventh Chords in the Melodic Minor Scale
In the harmonic and melodic minor scales, there are two types of sevenths that do not bear any accepted names because they are not frequently used in traditional music. In those cases, the type of triad and seventh interval is used to identify those chords.
