How were the constants chosen in round 2 and 3 in MD4?
I've got the solution myself in here

It says 


  SHA-1 was designed by NSA and uses the constants 5a827999, 6ed9eba1, 8f1bbcdc, and ca62c1d6. In case you haven't already noticed, these are hex representations of $2^{30}$ times the square roots of 2, 3, 5 and 10.