Chapter 19 mentions the author chanting the name of Rama. Does it also provide specific instructions from Sai Baba on a special mantra for the goddess Durga that should be chanted on Thursdays?

The provided text from Chapter 19 does not contain any instructions from Sai Baba about a special mantra for the goddess Durga. While the author does describe an experience related to chanting on a Thursday, the focus is entirely on the name of Rama. The author recounts making a firm resolve on a Thursday morning to do continuous chanting of Rama's name. As mentioned in Chapter 19, this decision was made after a wave of good thoughts arose upon waking, and the author felt the desire to test the truth in the saints' saying about nurturing such thoughts. The only deity mentioned for chanting in this personal story is Rama.