First, read the English article below.

Ovulation charts are useful for combining results from your vaginal discharge and basal body temperature (BBT) that can be used to identify trends in your cycle. Although you are having irregular periods, start the tracking on the first day of your period.  The first day of your period is day one. If your menstrual cycle is irregular, then you may bleed every 21-35 days for 2-7 days, perhaps with some spotting.  Number each of the days preceding your period. When you start a new period, then that is your new day one. Figure out the number of days your cycles approximately last for a few months. Then try to see if there is an average number that emerges as time passes. Create a chart that has temperatures ranging from 97.0 to 98.0 degrees Fahrenheit in increasing increments of 0.1 degrees on the X-axis and the days of your cycle on the Y-axis.  Put a dot on the temperature that corresponds your BBT reading under the corresponding day of your cycle. This way you can see if there are fluctuations from day to day in your BBT. Connecting the dots allows you to track trends more easily from a visual perspective. There is a drop and then a dramatic spike in your BBT when you ovulate, indicating the two most fertile days of your cycle. You can find a sample chart at BabyCenter.com. Create an easy to understand key describing your vaginal discharge. For example, D can indicate the dryness that occurs after your menstrual cycle, B can stand for a period, R can stand for regular white discharge, and F can stand for stringy, clear fertile discharge.  Compare your descriptions of your discharge against observations from previous cycles and see if your discharge changes consistency within an average range of dates. This can give you a better idea of how your irregular cycle lengths may vary. With irregular periods, it can be frustrating and hard to find patterns that indicate when you are most fertile. Your ovulation chart helps you see if there are certain trends that emerge. With irregular menstrual cycles, it can be... 

Now, please write a short abstract for it in Vietnamese. Abstract:
Bắt đầu vẽ biểu đồ trong ngày đầu tiên có kinh. Vẽ biểu đồ nhiệt độ của cơ thể mỗi ngày. Ghi thêm đặc điểm dịch tiết âm đạo từng ngày vào biểu đồ. Quan sát các mức trung bình trong các biểu đồ rụng trứng để nhận biết về thời điểm dễ thụ thai. Sử dụng biểu đồ rụng trứng để theo dõi độ dài của chu kỳ kinh nguyệt.