1) The swapping list is sorted in the following steps:

1.	Continent
2.	Country
2.	Territory / State / Province

2) In the column preceding the coordinates I indicate the accuracy of the sand collection place. Please see the links to the pdf-file on the main page or in the swapping Excel file.

3) Same Numbers with a different letter (e.g., 0156 and 0156a) are not sand variations of one collection site. They have an 'a' or 'b', because I received them from different people or collected them in two different years. Therefore, the collection date is different. Sometimes the collection site of one sample is more accurate than another but this will be indicated.

4) Three more explanations: In the first column I've indicated the amount of sand in ml I have of this sample:

• If there is a "0", I've recently swapped the last sample. But the new 'owner' will be able to view the information somewhat longer, in case my package takes a few weeks to go around the world.
• If there is a "500", I have more than one film container, but haven't calculated the exact amount.
• Each sample has at least the amount of 30 ml (or I've written the amount, for example, 26 ml). That's the reason I expect to receive 30 ml as well and not, for example, 20 ml. If you don't have 30 ml of a sample, please write the amount you do have in your swapping list; that's not a problem. Otherwise, it seems that you only want to increase the number of swapping samples.