61.   ...a letter of acceptance.

62.   He wrote a very formal letter of apology to Douglas.

63.   ...a stiffly worded letter of complaint.

64.   ...his letter of resignation.

65.   We received a letter of apology.

66.   We have received many letters of congratulation.

67.   Neil sent him a letter of condolence.

68.   ...a letter of grovelling apology.

69.   Many residents wrote letters of remonstrance to city officials.

70.   My boss wrote me a glowing letter of recommendation.