“…Audio records [14,21,31,64,65,71,81,102,109,112,131,148,160,161,182,202,207,211,220,250,273] Sound-related [35,56,64,76,103,112,174,211,212,214,220] Energy, entropy, spectral, jitter, shimmer, noise, Mel-frequency cepstral coefficients, perceived quality Representation characteristics (cues) [211,253] Instructor-related: verbal cues Visual features Video frames and images (figures and illustrations) [7, 14, 21, 29, 32, 38, 49, 50, 64, 65, 67, 72, 76, 80, 81, 83, 83, 102, 111, 111, 114, 115, 121, 123, 124, 131, 138, 148, 153, 158, 160, 161, 179, 182, 195, 198, 198, 207, 252, 255, 261-264, 264, 265, 273, 274, 274, 276] Representation characteristics (cues) [110,160,170,192,193,209,209,251,253] Instructor-related: pointing gestures, directed gaze. Content-related: highl...…”