context1: Once a public key has been uploaded, it is <strong>difficult</strong> to remove. Some users stop using their public keys for various reasons, such as when they forget their pass phrase, or if their private key is compromised or lost. In those cases, it was <strong>hard</strong> to delete a public key from the server, and even if it were deleted, someone else can upload a fresh copy of the same public key to the server.
context2: Because laminal consonants use the flat of the tongue, they cover a broader area of contact than apical consonants. Laminal consonants in some languages have been recorded with a broad occlusion (closure) covering the entire front of the mouth, from the <strong>hard</strong> palate to the teeth. Therefore it is <strong>difficult</strong> to compare the two: alveolar laminals and apicals are two different articulations.