The present invention provides methods for the production of a library of antigen specific antigen binding molecules having a peptide domain structure represented by the following formula (I): FW 1-CDR1-FW2-HV2-FW3a-HV4-FW3b-CDR3-FW4 comprising (1) isolating RNA from a member of a species in the Elasmobranchii subclass; (2) amplifying DNA sequences from RNA obtained; (3) selecting a DNA sequence from the database prepared; (4) amplifying DNA sequences encoding two or more contiguous peptide domains of FW1-CDR1-FW2-HV2-FW3a-HV4-FW3b-CDR3-FW4; (5) ligating together said amplified DNA sequences to form DNA sequences encoding an antigen specific binding molecule; (6) cloning the amplified DNA obtained into a display vector; and (7) transforming a host with said display vector to produce a library of said antigen specific antigen binding molecules. The invention also provides methods for the production of an antigen specific antigen binding molecule as defined, pharmaceutical compositions comprising such molecules and uses thereof in medicine.